Chance of pregnancy?

My fiancé and I were messing around about a week ago. We didn't have direct vaginal/penile intercourse though. I am on birth control, but I was on my first or second day of ovulation. He was unprotected. He went about an inch or two "inside" but it was more of a tease. We played around thrusting but he never actually penetated me. He was pre-cumming a lot and I was obviously very stimulated as well. I was on birth control but ovulating and I randomly started spotting a day or two ago. It's brownish and a very light flow! Like, extremely light. I was not expecting my period for another week and a half or so when this started. I have minor headaches and I want to eat everything. Could I be pregnant or could I just be having pre-menstural symptoms? Thanks.