Could I be pregnant?

I'm on the monthly shot and I'm missing my period, it was supposed to get it last thursday or saturday and nothing happened. Sometimes I got this late (sometimes for months) but this feels different. I've been crampy and despite my keto diet, I've gained almost 6 lbs in a week, I feel very anxious and sometimes sad, and my breasts feel fuller. A month ago I was on treatment with Amoxicillin because of my sinus and my period came two weeks early. Then I had *protected sex I guess* until I got my shot and had unprotected sex that same night. So, I don't know my chances. When I miss my period, I don't feel anything. Tomorrow I'll test but I want to know what to expect.