Don't know what to do

I was on the depo shot from October 26 to January 12th 2015 this was my first shot. I never went back. I started taking prenatal pills because my boyfriend and I are trying to conceive. I have taken ovulation tests and my highest was on February 15th. I have not had a period since December 19th. My question is on Wednesday had a brown spotting when I wiped there was nothing and have not seen nothing since. I recently had intercourse on March 3rd. Is it a possibility I am pregnant? Or is this normal? I've taken multiple tests and all negative