What Causes Early And Light Menstruation?

Hello. So I'm a young lady in my early 20s. I barely started to become sexually active 5 months ago. Always used a condom. 2 months ago I had sex after my period. Then the following month I got my period but I did not bleed much. It went from 5 days to 2 1/2 days. Then again I had sexual intercourse a week after my period, which was the last time I had sexual intercoursw. Now this month I again my period was 3 days early and only for 2 1/2 days. I don't know much about my period changing. Since I started my period I never had any changes. N my body feels strange lately. I don't know if it's because I've been eating late at nite a lot. Or because my changes in my period. My sex drive has also decreased. And the last time I had sexual intercourse, I was not into at all. Every time my partner tries to pleasure me I feel nothing much and a tingly feeling after around my stomach and in my uterus. I feel like maybe it's possible I can be pregnant but I think that is not.