Bleeding after ...have to do with pregnancy or not?

Okay, on February 14th I got my period which was bright red with minimal cramping (this is unusual because usually I have horrible cramps in my lower back). The next day, the 15th the bright red was gone halfway through the day, it seemed like my period had stopped. Then Tuesday the 16th came and there was a deep burgundy color that lasted until Thursday the 18th, (by the way all of the blood listed so far was only enough to fill up half a tampon). Friday morning I went to the bathroom and noticed a small amount of deep burgundy colored blood and was confused because I was supposed to have been off of my period. Friday night my boyfriend and I had (this was not our first time together) and when I got home I went to the bathroom to find a small, but noticeable, amount of bright red blood in my panties. I have no idea what that could be from because I wasn't bleeding before we had and I wasn't bleeding during . Could this be that he had "popped my cherry" even though I'm not a virgin and that wasn't our first time sleeping together? Could it be a pregnancy sign? Is it just because my period was weird? I have absolutely no idea what this is...my periods are usually very heavy and very regular and don't change color until the very very end...so I am very confused and pretty scared. I was told that it sounded like it wasn't my period at all but implantation bleeding so I'm wondering if you can bleed after in early pregnancy because your cervix is lowered. I have no idea...but anyone with advice or help of any kind would be awesome! Helpful answers only please! Thank you very much! Best wishes!