3 days late!

My period is 3 days late usually I’m pretty regular, I also feel very hot the last few days, have been very tired and irritated. I had mild cramping about two weeks ago and have been very gassy, my breasts are very heavy and hurt so bad I couldn’t sleep last night. My boyfriend and I had unprotected sex on the day this app said I was most fertile. Thoughts on this please! I have never been pregnant before and am anxious! I want to test but don’t want to do it too early.