Eu preocupo-me com o resultado do exame de amanhã.

The -me is a reflexive pronoun meaning “myself”.

• preocupar = to worry / to concern
• preocupar-se = to worry oneself, i.e. to be worried / to worry about (something)
• preocupo-me = I worry myself → I am worried / I worry

So Eu preocupo-me literally means “I worry myself”, which is how Portuguese forms the idea “I’m worried / I worry (about…)” in this structure.

This is a typical feature of European Portuguese: the object pronouns often attach to the end of the verb (with a hyphen). This is called enclisis.

• Eu preocupo-me com… – normal in European Portuguese
• Eu me preocupo com… – normal in Brazilian Portuguese, but sounds Brazilian in Portugal in this context

In European Portuguese, in an affirmative main clause with nothing “pulling” the pronoun forward, the default is:

verb + pronoun → preocupo-me

However, when certain words come before the verb (like não, também, que, etc.), the pronoun usually goes before the verb (proclisis):

• Não me preocupo com o resultado. – I’m not worried about the result.
• Também me preocupo com isso. – I also worry about that.
• Quando me preocupo, não consigo dormir. – When I worry, I can’t sleep.

So:

• European Portuguese (neutral context): preocupo-me
• Brazilian Portuguese (neutral context): me preocupo

Yes, you can absolutely drop Eu:

• Preocupo-me com o resultado do exame de amanhã.

In Portuguese, subject pronouns are often omitted because the verb ending already tells you who the subject is:

• preocupo = clearly “I” (1st person singular)

Including Eu:

• Eu preocupo-me…

can give a slight emphasis on I, for example in contrast to someone else:

• Eu preocupo-me com isso, mas ele não.
  I worry about that, but he doesn’t.

So both are correct; without Eu is more neutral and common in many contexts.

Portuguese makes a clear distinction:

• preocupar alguém = to worry someone / to cause someone worry
  
  • O exame preocupa-me. – The exam worries me.
• preocupar-se com algo = to be worried about something / to worry about something
  
  • Eu preocupo-me com o exame. – I’m worried about the exam.

So:

• non‑reflexive:
  
  • O resultado preocupa os alunos.
    The result worries the students. (The result is the thing that causes worry.)
• reflexive:
  
  • Os alunos preocupam-se com o resultado.
    The students are worried about the result. (They worry themselves about it.)

Your sentence is talking about your internal state, so it uses the reflexive form preocupar-se com.

With preocupar-se, the normal preposition is com:

• preocupar-se com algo = to worry about something

So:

• Preocupo-me com o resultado. – I’m worried about the result.

Other prepositions would be odd or have different meanings:

• preocupar-se sobre o resultado – not natural; sobre tends to be “about/concerning” in other contexts (e.g. falar sobre = talk about).
• preocupar-se por o resultado – ungrammatical; you almost never use por here.

So just memorise the pattern:

preocupar-se + com: worry about

do is simply a contraction of de + o:

• de = of / from
• o = the (masculine singular)
• de + o → do

So:

• do exame = de o exame = of the exam

Portuguese always contracts these:

• de + a → da (feminine singular) – da prova
• de + os → dos (masculine plural) – dos exames
• de + as → das (feminine plural) – das provas

You must use the contraction; de o exame written out is incorrect in standard Portuguese.

In o resultado do exame de amanhã:

• de amanhã is attached to exame ⇒ “tomorrow’s exam”
  Literally: the result of the exam of tomorrow → the result of tomorrow’s exam

If you just said:

• o resultado do exame amanhã

that would normally be understood as:

• the result of the exam tomorrow (the result will come tomorrow),
  not tomorrow’s exam.

So:

• o exame de amanhã = tomorrow’s exam
• amanhã o exame or o exame é amanhã = the exam is tomorrow (simple time adverbial)

Also note:

• amanhã = tomorrow
• a manhã = the morning
• de manhã = in the morning

Yes, that’s perfectly correct, and very common:

• Eu estou preocupado com o resultado do exame de amanhã.
  I am worried about the result of tomorrow’s exam.

Nuance:

• Eu preocupo-me com…
  – can describe a general tendency (I worry about it / it’s something that concerns me),
  – but in context it can also describe your current state.
• Estou preocupado com…
  – focuses more clearly on your current emotional state: I’m (feeling) worried right now.

In practice, to talk about how you feel now, many people in Portugal would use Estou preocupado com… slightly more naturally than Preocupo-me com…, though both are correct here.

In Brazilian Portuguese, the pronoun normally comes before the verb:

• Eu me preocupo com o resultado da prova de amanhã.

Changes you might see:

1. Pronoun position:

   • EP (Portugal): Eu preocupo-me…
   • BP (Brazil): Eu me preocupo…

2. “exam” word:

   • Portugal: o exame is very common.
   • Brazil: a prova is very common in the school/university context.
     ⇒ da prova (de + a = da).

3. Same preposition and structure:

   • preocupar-se com is still used:
     Eu me preocupo com o resultado…

Meaning is the same; the main obvious difference to the ear is me preocupo (Brazil) vs preocupo-me (Portugal).

In Portuguese, não comes before the verb, and in European Portuguese that pulls the pronoun in front of the verb too:

• Eu não me preocupo com o resultado do exame de amanhã.
  I’m not worried about the result of tomorrow’s exam.

Structure:

• Eu (subject)
• não (negation)
• me (pronoun)
• preocupo (verb)
• com o resultado do exame de amanhã (rest of the sentence)

No, not with this meaning.

• preocupar-se com algo = to be worried about something
  → needs the reflexive pronoun (me, te, se, nos, se).

Without the pronoun, preocupar normally means to worry someone / to cause worry:

• O resultado preocupa-me. – The result worries me.
• Esta situação preocupa os pais. – This situation worries the parents.

So:

• Eu preocupo-me com o resultado. ✅ I’m worried about the result.
• Eu preocupo com o resultado. ❌ incorrect for that meaning.

Here’s preocupar-se (present indicative) in European Portuguese, showing the typical enclisis (pronoun after the verb) in neutral affirmative sentences:

• (eu) preocupo-me – I worry / I’m worried
• (tu) preocupas-te – you worry (informal singular)
• (ele / ela / você) preocupa-se – he/she/you (formal) worry
• (nós) preocupamo-nos – we worry
• (eles / elas / vocês) preocupam-se – they / you (plural) worry

Examples:

• Preocupo-me com o resultado. – I’m worried about the result.
• Preocupas-te demasiado com isso. – You worry too much about that.
• Os alunos preocupam-se com os exames. – The students are worried about the exams.