Pregnant?

Okay so I had sex with my ex about 2 months ago and I got my period the first month (it was lighter than usual) but I had started a gluten free diet and had lost 15 pounds... And now I'm supposed to get my period again in 3 days but I'm stressing I won't. I have pms signs like sore boobs and light cramps and I'm tired but I'm freaking out and stressing. Can someone please ease my mind Bc I'm positive I'm not pregnant but I'm worried I am 😭