Pregnant without knowing??

Is it possible to be pregnant and not know it?
We have been TTC for 4 months now, I ovulated between February 28th-March 5th, i was 5 days late(took 3 HPT all BFN) but that evening (March 21) my period showed up, though it wasn't a normal period at all, lasted 2 days and was relatively light, and for almost 2 weeks I've been having to pee constantly and to be honest my water intake has actually been lower than usual, also I get very moody, breaking out more, and I feel bloated 24/7. 
Is it even possible to be pregnant and have what you think is a period??