Hi, I'm 21 Years Old And Haven't Had A Period

Hi, I'm 21 years old and haven't had a period for the whole month of July considering that the last day is tomorrow, I'm currently about ten days late. I've also been feeling a bit bloated, had very slight cramps in my belly, very very dark green stool, and slight nausea every now and then. Now, I've asked my mom and my boyfriend's mom and they both gave me generally the same answers. They basically told me it could be a number of things but pregnancy wasn't ruled out. But, here's where I'm confused, I've taken two tests the other day and they both came back negative. I guess I could have taken them too early but if I don't get my period by Wednesday then I'll go see a doctor. But, also, my boyfriend and I used a condom the last time we had sex. We didn't use one anytime before that so if I am pregnant then I'm guessing it happened before the 20th. I'm just a little desperate for a second opinion, thanks.