عندي صداع شديد

Just drop it into a sentence when you feel the pressure building. You do not need complex grammar here. If you are talking to a doctor, use it exactly like this. If you are at work, it explains why you are squinting at your screen. It is a complete thought on its own. You can also add 'because' after it to explain why. For example, 'because of the noise' or 'because of the light'.

Use it when the pain is actually bothering you. It is perfect for the office when you need a break. Use it with friends if you need to leave the party early. It works great at the pharmacy when asking for medicine. If you are texting a friend to cancel plans, this is your best excuse. It sounds serious enough that people will actually sympathize with you.

Do not use it for a tiny, dull ache that you can ignore. If you just feel a bit tired, this might sound too dramatic. Avoid using it as a metaphorical 'headache' (like a difficult person). In Arabic, we use different words for 'annoying' situations. This phrase is strictly for physical pain in your skull. Do not use it if you are just 'bored' or 'fed up'.

In many Arabic-speaking cultures, health is a common topic of conversation. People will often respond with 'Salamat' (get well soon). They might even offer you a cup of mint tea or lemon juice. It is very common to be open about physical discomfort. You will find that people are generally very sympathetic to health complaints. It is not seen as 'complaining' but rather sharing your current state.

If the pain is just 'okay', you can just say عندي صداع. If it is absolutely unbearable, you might say صداع قاتل (a killing headache). In some dialects, like Egyptian, you might hear دماغي بتوجعني (my head hurts me). In the Levant, people might say راسي عم يوجعني. However, عندي صداع شديد is understood by every single Arabic speaker from Morocco to Iraq. It is the 'Goldilocks' of phrases—perfectly understood everywhere.