Has this happened to anyone?!?

So I've taken a tone of tests, some said negative but then I finally got a positive, I'm three weeks late for pregnancy and I've been exhausted and having a few symptoms... I started to feel heavy cramping so my boyfriend and I went to after hours clinic, they did a urine test and it came back negative. They are sending me for a ultrasound and blood tests this week but we are both so disappointed we thought we were pregnant. Has this ever happened to anyone? I haven't spotted at all