My boyfriend and I have been working on having a baby. I haven't had a period this month, which should've started btw the 10th & 15th of this month, and its now the 27th. I'm still having some cramps here and there. I've taken 3 test which have come up negative, and after masterbating I get these wierd cramps like my uterus is tightening up or something. Tumor run in my family so I'm a bit nervous. What could this be?