Don't know what's going on....

April • momma of 3 beautiful boys!
So, I was supposed to get my period back on February 7th. When I didn't feel it coming at all, I decided to take a pregnancy test that day. It was negative. So I waited to see if it would come that weekend. When it didn't, I took another test a few days later, also negative. My doctor's office even gave me one that came up negative. I'm getting nervous though cause I still haven't gotten it, I've been feeling nauseous (but I've also been sick the last couple weeks...) and a few other things have been going on. I don't feel pregnant like I did with my other 3. I'm thinking about taking another test tomorrow, just to make sure. I really don't wanna be pregnant though as my doctor told me it wouldn't be a good idea due to all the scar tissue from my first c section and I developed preeclampsia after the birth of my last son and am still having problems with it. I'm freaking out!