Dün boynum ve belim ağrıyormuş gibi hissettim, bugün ise daha iyiyim.

Those are 1st person singular possessive endings, so they mean my neck and my lower back/waist.

• boynum = boyun
  • -(I)m → my neck
• belim = bel
  • -(I)m → my lower back / my waist

Turkish very often uses possessive forms with body parts when talking about your own body:

• Boynum ağrıyor. = My neck hurts.
• Belim ağrıyor. = My lower back hurts.

A small extra detail: boyun becomes boynum, not boyunum. This is because some Turkish nouns drop a vowel when a suffix is added.

In this sentence, bel usually means the lower back.

Depending on context, bel can also refer to the waist, but with pain or discomfort, English speakers will usually understand it as lower back:

• Belim ağrıyor. = My lower back hurts.

So in this sentence, boynum ve belim is most naturally understood as my neck and lower back.

This part means as if it was hurting / as though it seemed to hurt.

Breakdown:

• ağrı- = verb stem from ağrımak = to ache / hurt
• -yor = present continuous
• -muş = a form often associated with inference, appearance, or reported information
• gibi = like / as if

So:

• ağrıyor = it hurts / it is hurting
• ağrıyormuş gibi = as if it were hurting, as though it seemed to be hurting

In natural English, the whole phrase is often just translated as something like I felt like my neck and lower back were hurting.

Yes, ağrıyor gibi is possible too.

The version with -muş adds a little more distance, impression, or appearance. It can make the sensation sound a bit less direct and a bit more like:

• it felt as though...
• it seemed as if...

So:

• ağrıyor gibi hissettim = I felt like it was hurting
• ağrıyormuş gibi hissettim = I felt as if it seemed to be hurting / as though it were hurting

In everyday use, the difference can be subtle, but -muş gibi often gives a slightly more tentative or impression-based feeling.

Because the Turkish pattern X gibi hissetmek means to feel as if X or to feel like X.

• hissetmek = to feel
• hissettim = I felt

So:

• ağrıyormuş gibi hissettim = I felt as if it was hurting

This is a very common structure in Turkish:

• Yorgun gibi hissettim. = I felt tired.
• Hasta olacakmışım gibi hissettim. = I felt as if I was going to get sick.

Yes, but the meaning changes.

• Dün boynum ve belim ağrıyordu. = Yesterday my neck and lower back were hurting.
• Dün boynum ve belim ağrıyormuş gibi hissettim. = Yesterday I felt as if my neck and lower back were hurting.

The first version states the pain more directly as a fact.

The sentence you were given is a little softer and more subjective. It focuses on the speaker’s sensation or impression, not a firm statement about actual pain.

Here ise marks a contrast. It is like saying:

• as for today
• today, however
• today though

So the sentence contrasts yesterday with today:

• Dün ... hissettim, bugün ise daha iyiyim.
• Yesterday I felt ..., but today I’m better.

It is not exactly the same as ama, but in many contexts both give a contrastive feeling.

Compare:

• ama bugün daha iyiyim = but today I’m better
• bugün ise daha iyiyim = today, however, I’m better

The version with ise sounds a bit smoother and more topic-contrastive.

Because Turkish often leaves out subject pronouns when the verb already shows the person.

• hissettim already means I felt
• iyiyim already means I am well / I’m better

So ben is not necessary.

If you add ben, it usually gives extra emphasis:

• Ben bugün daha iyiyim. = I am better today (with emphasis on I)

In normal speech, leaving it out is completely natural.

Both can work, but they are slightly different.

• daha iyiyim = I am better
• daha iyi hissediyorum = I feel better

In Turkish, iyi olmak is very commonly used where English might say either be well or feel better.

So bugün ise daha iyiyim is perfectly natural and idiomatic.

Also, iyiyim is a present-state form, so it matches the idea of how I am today.

Because it talks about two different times:

• Dün ... hissettim = Yesterday I felt... → past
• bugün ise daha iyiyim = today I’m better → present

This is very normal in Turkish. The speaker is comparing:

1. how they felt yesterday
2. how they are today

So the tense change is exactly what you would expect.

Yes, it is very natural Turkish word order.

First clause:

• Dün = time expression first
• boynum ve belim = subject/topic area
• ağrıyormuş gibi = descriptive phrase
• hissettim = verb at the end

Second clause:

• bugün ise = contrastive time/topic
• daha iyiyim = predicate

Turkish often places the main verb or predicate toward the end of the clause, so this sentence is quite typical.

The ğ in Turkish usually does not sound like a hard English g.

In ağrıyormuş, it mainly affects the flow of the vowels rather than adding a strong consonant sound. A simple learner-friendly approximation is:

• ağrıyor ≈ aa-rı-yor
• ağrıyormuş ≈ aa-rı-yor-mush

So do not pronounce it like ag-ri-yor-mush with a hard g.

Also, ş is pronounced like sh in English, so:

• muş sounds like moosh / mush depending on how you approximate Turkish vowels.