3 weeks!!

I'm wondering if I'm actually pregnant!! My husband and I are trying to conceive and some days I feel pregnant and some days I don't. I'm really tired all the time and have stomach cramps like I would if I had my period. I've been using the restroom a little more than usual. I've also been a little moody. I had my last period May 21 and according to this I am 3 weeks pregnant. Could I be pregnant??