Why is my menstrual period lasting 15 days?

Menstrual migraines can be caused by changes in hormones and dehydration. Over-the-counter painkillers are generally safe to take for a headache but make sure it is suitable for use during your period before taking anything new. Always follow the directions on over-the-counter medication or ask a pharmacist which ones won’t interfere with menstruation. 

It's common for cycles to vary a bit now and then due to factors like stress, diet, or lifestyle changes. So, the change to a 36-day cycle this time is likely just your body adjusting. Now, based on a typical 28-day cycle, your fertile window could be around December 10-15. However, since your cycle is longer this month, it might shift slightly. So, for the best chance to conceive, aiming for intercourse around December 8-17 would be a good plan. These are just estimates, and every body is different, so staying in tune with your body's signals is key. 

There is still the possibility of getting pregnant if you have had unprotected sex three days before your period is due. This is because sperm can live for a few days inside the body. Not having your period might be a sign that you are pregnant. If you’re worried, after missing a period you can take a pregnancy test to find out for sure.