Is this it?? Or is it impossible?

The last time I tried was on the 27th of Febuary. I had light brown spotting a couple days later but i got my period on the 12th. RIGHT ON TIME. It was not as heavy and it was 4 days instead of 5. As soon as i got of my period, i started having frequent headaches, nausea, and cramping. I felt like i was stilll on my period. I've been on a diet (my boyfriends a nutritionist) for a month. And I havnt lost any weight!! I lost 5 at the end of feb, and now i gained 7 because im always hungry!! I have white discharge and I havnt had the urge to have for 3 weeks now. BUT I GOT A BFN LAST NIGHT. Can i still be pregnant?? Ive been trying for 2yrs and this is the first time ive felt this way.