Missed Period

So I had a miscarriage November 2015. I then proceeded to bleed almost everyday for 6 months I went back to my doctor and they said everything is fine and they put me on birth control to get my periods regular again when I got off i proceeded to not have any bleeding for 2 months called and made an appointment and they checked me all out and said I am fine but put me back on birth control to get my periods back I got off 2 months ago normal period I am now around 15 days late for the next one and I have taken 2 test and both are negative. I'm at the point that I'm tired of going to the docs just to be told your fine here's some birth control to regulate.  I have been super nauseous as well any advice?