Am I psyching myself out?

I've been on the NuvaRing for 3 years. Last month after my period I decided not to but the ring back in, because I had not been sexually active in over a year and I'd felt it was depressing me.

About a week ago, I had unprotected sex, but it was only for a couple of minutes. My partner did not orgasm and we stopped quickly because we did not have a condom.

I know it was only a week ago, but for about a week now (I have terrible memory, I can't recall if this was happening before) I've had extremely sore/tender nipples. They hurt so bad I can barely lie on my stomache.

Also for a few weeks I've had pretty bad cramps.

I don't believe I am pregnant...so my question is, can the reason behind my discomfort be because my body is trying to get back to the way it was before birth control?

Also, my last period was early in July and I still haven't had one since I've been off of birth control.

Any advice, stories, or suggestions would be great. :-) Thanks.