So on the 29th me and my boyfriend had sex and he came in me for the first time, we always have unprotected sex but he always would pull out, my period would always come around the 25th but then in January it changed to the 14th then in feb it changed back to the 25th, this month I haven't had my period yet, I took a pregnancy test on the 28th and it was negative but me and my boyfriend did it on the 29th and the 30th and both times he came inside me, I went to the bathroom today and when I wiped there was a light red blood on the toilet paper, I read that implantation bleeding happens 10-12 days after... what could this be then?

You wouldn't experience implantation bleeding from sex on the 29th and 30th of March as that would be too soon. IF you happened to ovulate around that time, and IF the egg happened to become fertilized, it would be several more days before implantation might occur... (rough guide is 6-12 days after conception). While some women do notice a bit of spotting with implantation, the majority of women won't notice a thing.

It's likely that the spotting you've noticed is from the recent sex. Certainly, pregnancy can happen since you are having sex, especially with it being unprotected, so be sure to be taking a good multivitamin with at least 400 mcg of folic acid, or you can take folic acid on it's own. This is important when trying to become pregnant, and even when you're not trying to, but are having sex as pregnancy will be a possibility. Folic Acid can help to prevent certain birth defects that can occur very early in a pregnancy, sometimes before a woman even knows that she is pregnant.

It may just be an off cycle, and your period will show up late or you may skip a month, but if you don't have a period in several more days, try another test, as pregnancy can be possible from a previous encounter.