Με πονάει ο σβέρκος μου όταν κάθομαι πολλές ώρες στον υπολογιστή.

Because Greek often expresses this idea as something hurts me.

So in Με πονάει ο σβέρκος μου:

• με = me
• πονάει = hurts
• ο σβέρκος μου = my neck / the back of my neck

Literally, it is closer to:

• My neck hurts me
• or The back of my neck hurts me

This is a very common Greek pattern with body pain:

• Με πονάει το κεφάλι μου = My head hurts
• Με πονάει η μέση μου = My lower back hurts
• Με πονάνε τα πόδια μου = My legs hurt

You can also use πονάω / πονώ in other structures, but for specific body-part pain, με πονάει + body part is extremely natural.

Because ο σβέρκος μου is the subject of πονάει.

In other words, the thing doing the hurting is the back of my neck:

• ο σβέρκος μου = subject
• με = object (me)

So grammatically, Greek treats the sentence like:

• The back of my neck hurts me

That is why σβέρκος stays in the nominative:

• ο σβέρκος μου

not:

• τον σβέρκο μου

Σβέρκος means the back of the neck, the nape, or sometimes more loosely the neck area at the back.

It is not quite the same as the more anatomical/formal word:

• αυχένας = neck

A useful distinction is:

• σβέρκος = the back of the neck, more everyday/colloquial
• αυχένας = neck, more neutral or medical/formal

So this sentence specifically refers to pain from sitting at a computer, which makes σβέρκος a very natural choice.

In Greek, possessive phrases usually still take the definite article.

So Greek says:

• ο σβέρκος μου = literally the neck of-me / my neck
• το κεφάλι μου = my head
• τα χέρια μου = my hands

This is normal Greek structure. Unlike English, where my usually replaces the, Greek often uses:

• article + noun + weak possessive pronoun

So ο σβέρκος μου is exactly what you would expect.

Μου here means my, but grammatically it is a weak genitive pronoun.

Greek commonly expresses possession like this:

• ο φίλος μου = my friend
• το σπίτι μου = my house
• ο σβέρκος μου = my neck

So instead of a separate possessive adjective like English my, Greek often uses these short pronouns after the noun:

• μου = my
• σου = your
• του / της = his / her
• μας = our
• σας = your
• τους = their

This post-noun placement is one of the most common Greek possession patterns.

Because the subject is singular:

• ο σβέρκος μου = my neck / the back of my neck

So the verb is singular too:

• πονάει = hurts

If the subject were plural, the verb would usually be plural:

• Με πονάνε τα πόδια μου = My legs hurt
• Με πονάνε τα μάτια μου = My eyes hurt

So the verb agrees with the body part that hurts, not with με.

Κάθομαι literally means I sit / I am sitting, but in many contexts it also means:

• I stay sitting
• I spend time sitting
• I sit for a while / for long periods

So in this sentence:

• όταν κάθομαι πολλές ώρες στον υπολογιστή

it means something like:

• when I sit at the computer for many hours
• when I spend many hours sitting at the computer

That is very natural Greek. It does not have to mean the simple act of lowering yourself into a chair; it can describe the ongoing state of being seated.

Because Greek can use the accusative directly to express duration of time.

So:

• πολλές ώρες = for many hours

This is a very common pattern:

• Δούλεψα δύο ώρες = I worked for two hours
• Περίμενα πολλή ώρα = I waited a long time
• Κάθομαι πολλές ώρες = I sit for many hours

You can sometimes also hear για πολλές ώρες, but the version without για is very standard and often more straightforward.

Yes, literally it is on the computer, but idiomatically it often means:

• at the computer
• on the computer
• using the computer

Στον is a contraction of:

• σε + τον = στον

So:

• στον υπολογιστή = at/on the computer

This is a normal Greek way to talk about computer use:

• Είμαι στον υπολογιστή = I’m at the computer / on the computer
• Κάθομαι στον υπολογιστή = I sit at the computer

English and Greek package this idea a little differently, but the meaning is natural.

Όταν means when and introduces a time clause.

So:

• όταν κάθομαι πολλές ώρες στον υπολογιστή = when I sit/spend many hours at the computer

This tells you the circumstance under which the pain happens.

A useful point: Greek uses the present tense after όταν quite naturally when talking about repeated or general situations:

• Όταν διαβάζω πολύ, κουράζομαι. = When I study a lot, I get tired.

So in your sentence, the present tense suggests a habitual situation, not just one single event.

Yes. Greek word order is more flexible than English, because case endings and pronouns help show who is doing what.

The original sentence:

• Με πονάει ο σβέρκος μου όταν κάθομαι πολλές ώρες στον υπολογιστή.

is very natural.

But you could also hear things like:

• Ο σβέρκος μου με πονάει όταν κάθομαι πολλές ώρες στον υπολογιστή.
• Όταν κάθομαι πολλές ώρες στον υπολογιστή, με πονάει ο σβέρκος μου.

These versions are all understandable, but the emphasis shifts a little:

• starting with Με πονάει foregrounds the experience of pain
• starting with Ο σβέρκος μου foregrounds the body part
• starting with Όταν... foregrounds the condition or time

So the original is not the only possible order, just a very idiomatic one.

It is mostly neutral everyday Greek, with one slightly colloquial element:

• σβέρκος is everyday and a bit more colloquial than αυχένας

Everything else is completely standard and natural.

A more formal or medical version might use:

• Με πονάει ο αυχένας μου όταν κάθομαι πολλές ώρες στον υπολογιστή.

That sounds a bit more like something you might say to a doctor or see in health-related writing.

The original sentence sounds like normal spoken Greek.