Late and negative pregnancy test.

Last week I took two pregnancy test before my missed period. I was suppose to start on the 7 and didn't and tested again today and still negative. I don't feel like I'm going to start my period right now either. I'm usually cramping really bad and start either later that night or early the next morning. Should I go get a blood test?? I have had mild hot flashes and little nausea but nothing major and my boobs are a little sore. This is the third month we've tried getting pregnant and I feel hopeless. I didn't have any problems with my first child. I guess I'm just being impatient. Please help!!!