I've noticed a pattern in my LTR. Things go great for a couple weeks, gf is being feminine and sweet and a little needy. Then, within a week to 10 days of her period starting, she gets kind of distant. I try to stay steady and not act any different, and then she starts asking if I'm ok or why am I seeming distant. I just make a little joke and say nothing is wrong. This carries on until her period starts and then it all starts over again.

Should I be doing anything different? Is this just typical female hormones?