Many thanks for your question. The UK Medical eligibility criteria rank all health problems in relation to different types of contraception as 1,2,3 or 4.
Ranks 1 and 2 generally mean that the benefits outweigh the risks.
Ranks 3 and 4 generally mean that the risks outweigh the benefits.
A history of migraines with aura more than 5 years ago at any age is ranked as a 3 - that is the risks outweigh the benefits of the combined pill.
Current history of migraine with aura is a 4 that is completely contraindicated.
People tend to be very careful about migraines as they increase your risk of stroke - and so does the pill. Separately these risks are very small indeed, but combined they become much more significant.
Hope this is helpful.