What Causes Vaginal Spotting With No Regular Period?

I had a period, 7 days long, normal to heavy flow in June. 2-3 weeks later, after ovulation my boyfriend and I had sex multiple times within a three day time period. He didn t wear protection nor did he pull out. He came every single time. Waited for my period to come and I was two days late. I went to the bathroom and I was lightly spotting, brownish/red in color. It lasted for 4 days then stopped. This month, I spotted for 5 days. Could I be pregnant?