Confused..

I feel.. Different I don't know to explain it.. I could be pregnant, not rightly sure but the symptoms like back pain and sleeping a lot have always been there because I have scoliosis pretty badly and always have lower back pain, I sleep A LOT. But I've had gas, I've also had small cramping randomly on my right pelvic side and I've felt nauseous today, I almost threw up in the library when I was studying because I could smell someone's food across the room. I was spotting for 3 months on the depo shot, it was supposed to be out of my system the 26-27th but my BF and I had unprotected sex and it stopped like an hour after and hasn't started since on the 28th and my fertile window was there. But my friend told me that the depo shot takes 90 days (if you don't get another shot-- I only had one) after the first dose and it's not likely I am. But idk my body just feels.. Different. Random opinions would be appreciated. If I keep feeling like this I'm going to take a test in a week or so but I'm just up late wondering. Thank you!