Δεν είναι φυσιολογικό να πονάς τόσο πολύ, πρέπει να μιλήσεις με γιατρό.

Greek often does not use a dummy subject like English it in sentences such as It is not normal....

So:

Δεν είναι φυσιολογικό να πονάς τόσο πολύ
literally works more like
Is not normal for you to hurt so much

In natural English, we need it, but in Greek the structure works without it.

Because Greek commonly uses the neuter singular adjective in impersonal expressions.

Here, φυσιολογικό means normal in a general, abstract sense, not describing a masculine or feminine noun. It is basically the default form used in sentences like:

• Είναι καλό να ξεκουράζεσαι. — It is good to rest.
• Δεν είναι εύκολο να το κάνεις. — It is not easy to do it.
• Δεν είναι φυσιολογικό να πονάς τόσο πολύ. — It is not normal for you to be in so much pain.

So φυσιολογικό is not agreeing with a visible noun; it is being used impersonally.

Να is a very important Greek particle that introduces the subjunctive.

It often appears after verbs or expressions like:

• πρέπει να — must / should
• θέλω να — I want to
• μπορώ να — I can
• είναι καλό να — it is good to

In this sentence:

• να πονάς = for you to be hurting / that you be hurting
• να μιλήσεις = for you to speak / that you speak

There is no single English word that matches να perfectly. Sometimes it corresponds to to, sometimes to that, and sometimes English just uses a different structure entirely.

Πονάς is the 2nd person singular form, so it means you hurt / you are in pain.

The speaker is talking to one person informally:

• πονάω / πονώ — I hurt
• πονάς — you hurt
• πονάει / πονά — he/she/it hurts

After να, the same non-past form is used:

• να πονάς — for you to be hurting

If the speaker were addressing more than one person, it would be:

• να πονάτε — for you all to be hurting

Formally, after να, Greek uses a subjunctive form rather than an ordinary indicative present. But in many verbs, the form looks the same as the present.

So πονάς by itself can mean:

• you hurt / you are hurting

and after να:

• να πονάς = for you to be hurting, that you be hurting, or more naturally in English, just to be hurting

In this sentence, it refers to an ongoing situation: the person is experiencing pain.

Τόσο πολύ means so much, so badly, or that much.

The two words work together:

• τόσο = so / that much
• πολύ = much / a lot

So πονάς τόσο πολύ means you are hurting so much or you are in so much pain.

Greek often combines them this way for emphasis. It is completely natural.

Compare:

• πονάς πολύ — you hurt a lot
• πονάς τόσο πολύ — you hurt so much

The second one is stronger and more emotional.

Πρέπει can mean must, have to, need to, or should, depending on context.

In this sentence:

πρέπει να μιλήσεις με γιατρό

it most naturally means something like:

• you should talk to a doctor
• you need to talk to a doctor

It sounds like strong advice, not just a mild suggestion.

So πρέπει is often stronger than English should, but not always as absolute as must.

Because after πρέπει να, Greek often uses the aorist subjunctive when talking about a single, complete action.

• να μιλήσεις = to speak / to have a conversation / to talk once
• να μιλάς = to be speaking / to speak regularly or continuously

So:

• πρέπει να μιλήσεις με γιατρό = you need to talk to a doctor
  one concrete action

Whereas:

• πρέπει να μιλάς με γιατρό συχνά = you need to talk with a doctor often
  repeated or ongoing action

This is a very common Greek distinction.

Yes, με often means with, but with the verb μιλάω / μιλώ it is also the normal way to express talk to / talk with someone.

So:

• μιλάω με τον φίλο μου = I talk to / with my friend
• μίλησε με τη μητέρα σου = talk to your mother
• να μιλήσεις με γιατρό = to talk to a doctor

This is one of those places where Greek and English use prepositions differently. Even though με literally means with, the natural translation here is often to.

Both are possible, but they feel slightly different.

• με γιατρό = more general, slightly compressed, common in advice-like speech
• με έναν γιατρό = with a doctor, more explicit
• με τον γιατρό σου = with your doctor, specific doctor

A learner will very often hear or use:

πρέπει να μιλήσεις με έναν γιατρό

and that is perfectly natural.

The version without the article is still understandable and natural enough in context, especially in speech, but με έναν γιατρό is often clearer for learners.

In everyday Greek, γιατρός usually means a medical doctor.

So in this sentence, it clearly refers to a medical professional, not someone with a doctorate degree in the academic English sense.

If the sentence says:

πρέπει να μιλήσεις με γιατρό

the intended meaning is definitely you should talk to a doctor.

The comma is natural in everyday Greek because the two parts are closely connected:

• Δεν είναι φυσιολογικό να πονάς τόσο πολύ
• πρέπει να μιλήσεις με γιατρό

The second clause follows directly as a conclusion or recommendation.

In careful writing, a full stop would also be fine:

Δεν είναι φυσιολογικό να πονάς τόσο πολύ. Πρέπει να μιλήσεις με γιατρό.

Both versions work. The comma makes it feel like one flowing statement.

Yes, you might hear that, but it is slightly different in feel.

• Δεν είναι φυσιολογικό να πονάς τόσο πολύ sounds more general and standard in this context.
• Δεν είναι φυσιολογικό που πονάς τόσο πολύ sounds more like commenting on the fact that you are in so much pain.

In many real situations, both are understandable, but να πονάς is the more typical structure after είναι φυσιολογικό.