My FitBit tells me that my average sleep time is 7.5 hours. That's pretty good for me since I'm a light sleeper. My girlfriend moving in bed wakes me up. Worse

My FitBit tells me that my average sleep time is 7.5 hours. That's pretty good for me since I'm a light sleeper. My girlfriend moving in bed wakes me up. Worse than that is that if I do have a lie in, or I sleep longer than 8 hours — yes, I recorded sleep before my FitBit — I'd end up with headaches all day and night, worsening my sleep the next night. 7.5 hours seems to be my perfect sleep duration. I've never been able to have a lie in, even when growing up with my parents and going through puberty. I'd want to lie in, but my parents would have me up by 8:30 every day. 9AM on rare occasions. I wonder if that's got anything to do with it.