What Can Be The Reason For Delay In The Periods?

Hi I recently went off birth control about 6 months ago from chronically using it for 7 years. I have been getting regular periods 6 weeks apart since stopping, but after my last period of feb 28th ive seems to stop getting a period. I have missed two now and have been getting light cramps that feel like my period is coming but it doesnt. Ive also been having a loss of hunger. I have taken 7 HPT and all have been negative, is it possible that I could be pregnant although the urine test this morning was negative?