symptoms but negative tests.

I've had sex multiple times with my boyfriend. (Don't use condom but never finishes inside of me.) I know it's still possible because of precum. I've been experiencing symptoms. Back pain, headaches, dizziness, cramping, fatigue. But also a couple days after my period was supposed to start, I started to bleed like a period. But it only lasted 1 1/2 days, which is unusual for me. I've taken two tests. Both negative. But I still feel like there's something happening with my body. Couple I be pregnant? Or am I just overthinking? When should I take another test?