Estou com dor na barriga desde o almoço.

In Brazilian Portuguese, a very common way to talk about physical states is:

estar com + noun

So:

• Estou com dor = literally I am with pain
• natural English meaning: I have a pain / I’m in pain

This pattern is extremely common:

• Estou com fome = I’m hungry
• Estou com sono = I’m sleepy
• Estou com febre = I have a fever
• Estou com dor de cabeça = I have a headache

You may also hear Tenho dor... in some contexts, but estar com dor is the most natural everyday phrasing here.

Because the sentence describes a temporary physical condition, not a permanent characteristic.

• estou comes from estar, used for states and conditions
• sou comes from ser, used for identity, essential traits, and more permanent descriptions

So:

• Estou com dor na barriga = I have a stomachache / My stomach hurts
• Sou... would be wrong here

A pain or stomachache is something temporary, so estar is the correct verb.

Dor = pain
Barriga = belly, tummy, stomach area

So dor na barriga means pain in the belly/stomach area.

In natural English, depending on context, it could be translated as:

• stomachache
• stomach pain
• my stomach hurts
• belly pain

It is a common, everyday way to describe abdominal discomfort.

Na is a contraction of:

• em
  • a = na

Here it means in the or on the stomach/belly area.

So:

• dor na barriga = pain in the belly
• literally: pain in the belly area

Portuguese often uses a preposition where English may use a possessive or a simpler noun phrase.

Compare:

• dor na cabeça = pain in the head / headache
• dor nas costas = back pain
• dor no peito = chest pain

Portuguese often does not use possessives like my, your, his, etc. when the context already makes it clear whose body part is being discussed.

So instead of saying something equivalent to my belly, Portuguese often just says:

• na barriga
• literally in the belly

Because estou already means I am, it is obvious that the speaker is talking about their own belly.

This is very common with body parts:

• Lavei as mãos = I washed my hands
• Estou com dor na cabeça = I have a headache
• Machuquei o braço = I hurt my arm

Not exactly.

• barriga usually refers to the belly or abdomen in a general, everyday way
• estômago refers more specifically to the stomach as an organ

In casual speech, if someone feels digestive discomfort, nausea, cramps, or a stomachache, they will often say dor na barriga.

If you say dor no estômago, it can sound a bit more specific or medical.

So:

• dor na barriga = very common, everyday
• dor no estômago = also possible, but more anatomically specific

Desde means since.

So:

• desde o almoço = since lunch / since lunchtime

It tells you the pain started at or around lunchtime and has continued until now.

Structure:

• desde = since
• o almoço = lunch

This is a very common way to express duration from a starting point up to the present.

Examples:

• Estou aqui desde cedo. = I’ve been here since early morning.
• Não como desde ontem. = I haven’t eaten since yesterday.

Because almoço is a masculine noun in Portuguese:

• o almoço = lunch

After desde, Portuguese normally uses the definite article when referring to a meal or time point in this way:

• desde o almoço = since lunch
• desde o jantar = since dinner

This sounds natural in Portuguese, even though English often leaves out the.

Portuguese commonly uses the present tense to describe a state that began in the past and is still true now, especially with desde.

So:

• Estou com dor na barriga desde o almoço.
• literally: I am with stomach pain since lunch
• natural English: I’ve had a stomachache since lunch / My stomach has hurt since lunch

This is a very important difference between English and Portuguese.

More examples:

• Moro aqui منذ 2020. would be wrong because that has Arabic script? Need avoid typo. Let's fix in final? I need ensure no mistakes. Let's continue carefully. We must not include typo. We'll rewrite answer fully.