what could this be

I had protected sex with my bf on sept 7, and I was super anxious for 10 days about being preganant, dissecting every symptom. Then I got my period on sept 17th, and it left after 6 days and it was heavy. Ever since then I've been having spells of nausea and dizziness, but that decreased after like sept 30. But the last few days I'm having cramps (like period feeling cramps) and burning sensation and Lower and upper back pain quite a few times a day. I also took 7 tests Bc that's how nervous I was (throughout the last few weeks) and they were all negative, so if I'm not pregnant what the heck is going on?? It was also my first time in a couple years and he went all the way which my ex never did. I'm just confused about why I'm still feeling weird a month later, luckily I have a dr appt on the 17th, but I was just wondering about other ideas or opinions until I go. Any input helps😊