am I preggs?

Bi
My last period was between March 31-April 2. Only lasted three days and was lighter than usual. According to this app I should have had 2 cycles since then but I have not bled one drop. Also- after missing the first period I had a bit of clear discharge whenever I would visit the ladies room. I've taken a test about every other week that goes by and they come back negative. If I'm not pregnant what could be delaying my period????
Side note I've been nauseous every single day. When I wake up and when I eat I almost always feel gross. 
Help!