Period cramps with no period??

So first off, im on nexplanon and have been for aviut 2 1/2 years. It goes out in November. My most recent bf and I have stopped using condoms and we've agreed that it should be ok if he bust in me. And its become a regular thing. With my birth control, i hardly ever have my period. Like its be a few months in between. Or more. But since I've gotten in a relationship with so much more emotion and stuff, theres been a lot more sex. And my period has started back on every month it would seem. I ended my last peroid about a week ago. Maybe a day or two more. Then last Tuesday left on a trip with my bf and some friends to go across country for a music festival. It was 5 days long and we just got back today. We were camping in the woods. And watching a lot of concerts, i smoked a lot of weed and had a blast. This was my first time so far from home and doing anything like this. I didnt do anything crazy. The most i drank was like 1 shot and a swig of a mix drink which i didnt feel. But the last 2 days of the festival i noticed i was getting what felt like period cramps. I thought this may be from me holding my piss so much while there because the porta pottys were awful and there were a lot of people in the woods. But nothing else vurned plus i was taking some azo to help which normally works right away. Late last night at the last concert for the frstival i believe i started my period. When i got back to my tent i checked for blood but there hardly any there. And it wasn't fresh at all. And its continued today. It would seem im hardly spotting at all. But its still happening. Normally my flow starts full throttle and doesnt get like this until the last day. And the first day of cramps there was no blood. The second day i didnt start bleeding until really late that night. And the cramps are coming in like waves. They're not excruciating but damn uncomfortable. Does anyone have any clue what could be happening to me?