Could I be pregnant?

I'm four weeks late and we've taken a couple pregnancy tests one was negative but when another week went by we took another one and it was a faint positive. I started to feel exhausted all the time, having crazy dreams, and frequently peeing, but then I started to cramp on my lefthand side, and when it didn't go away I went to Doctors and told him about it. When they did a pregnancy test on me it came up negative so now they have me getting an ultrasound tomorrow as well as a blood test but I haven't spotted at all. Is it possible to be pregnant? Or are my hormones just out of wack