LATE PERIOD?

Okay so I’m 16 and I’ve have a change in my cycle lengths when I became sexually active, I went from cycles of 28-30 days to 32-34 day cycles, and that’s all fine and dandy but this time it’s cycle day 38. My boobs hurt, I’m getting emotional, my lower back hurts, I have crotch and leg cramps, I’m bloated and super hungry. I took a pregnancy test and it came back negative but the control window was blank so I have to take another, although my boyfriend and I are extremely careful when it comes to sex so maybe it’s late cause of stress? Idk any ideas?