I Had Protected Sex 3 Days Ago, It Was My

I had protected sex 3 days ago, it was my first time. I lost my virginity, I didn't bleed or anything, it felt normal, however it did kind of hurt when he tried to go harder so I made him stop. I didn't think anything was wrong, but recently yesterday I experienced rednlight blood I thought my period started early and then today the second day I experienced some light brownshish discharge, on my calendar it's a week before my period but my periods are very irregular. I've been going through very serious stress and anxiety about pregnancy ever since 2 days ago when I actually had sex. I'm freaking out because I keep thinking it's implantation bleeding ? But what else can I get that from ?