The noun “migraine” can be both countable and uncountable.
The noun “migraine” can be both countable and uncountable, so we can say:
Did you have migraine during pregnancy?
I had a migraine last Friday.
However, the more precise or specific you are to describe a migraine (in terms of location, intensity, etc.), the more likely you will use a/an.
I had a severe migraine last week.
But omit the article to speak about this symptom in a general sense.
Some people suffer from migraine.
Similarly, we never include the article when using the plural form (migraines) in a general sense.
Migraines are more common in women than in men.
When listing a series of symptoms, we also tend to omit the indefinite article "a".
I have migraine, nausea, and fever.