Is this normal with the implant?

I got the birth control implant inserted about 5 weeks ago. 3 weeks later I got my period, it seemed normal, but maybe lasted a little longer that usual, then I had about a week with no blood or anything. That brings us to this last week.

I've had sex with my boyfriend a couple of times this week and he came in me. I only recently lost my virginity and still have pain in some positions (he's been very patient with me though, and I've been using dilators to help relax myself which have definitely helped)

Anyway after the sex this week, the next day I had some blood, I thought that maybe it was just from the sex and maybe it hurt my insides a little bit, but then the next day I had cramps in addition to the bleeding. Its now 3 days since we had sex and these 3 days it kind of feels now like I've started my period again, I'm using a tampon now. I only started my last period about 16 days ago though.

Is this normal? Could I be on my period again after just 2 weeks? I'm afraid that it could be something serious but I'm trying to think rationally and about the fact it's still within my first couple of months with the implant.