I had sex for the first time with my boyfriend, I'm on birthcontrol. We had sex on March 27th right after my period ended, however today I'm spotting and wondering if that's due to implantation bleeding or if its possible from not having sex that I possibly had a vaginal tear, because my vagina also feels swollen

Yes, yes and yes, it could be those or other issues.

As you are aware birth control is not 100 percent, so there is always a chance. But it is most likely another issue