Pregnant? Not pregnant?

So I’m 13-14 days late on my period, My fiancé and I are trying we had sex on the 19th of July. I’ve have been cramping for the past week-week and half, I have slight nausea in the afternoons, and the last couple days I’ve been getting a headache that randomly hits and I get dizzy and it goes away in about 15-25 minutes. I have taken 2 pregnancy test one the week before my period was to start and one at 2 days late, both were negative. He’s wanting me to go to the doctor tomorrow because I have been having an upset stomach/light nausea, and I don’t want to waste that money on a burnt run.