There was some pre-cum but actual penetration has not occurred

HELP, am I Pregnant???

About 8 days ago my bf has fingered me after touching his penis outside my vagina. There were some pre-*** but actual penetration has not occurred. I'm concerned that his actions caused the small amount of pre-*** to be pushed further in, resulting in a higher chance of any existing sperm within his pre *** to impregnate me. HOWEVER, this is the part that worries me.. About a little over 2 days ago I have began what I thought was my period. It was light and brown at first, but developed into a heavy dark red like a period, but suddenly stopped before hitting day 3. There was minimal cramping as well. What confuses me is that I am almost NEVER regular with my periods. If I haven't engaged in any penis related activity I probably wouldn't have worried about my short time period as I had them before without any contact with a penis.. Please help, I'm very stressed over this. I wouldn't be surprised if the stress alone caused my weird period! Some additional notes: I am a virgin, I normally skip periods, sometimes they're light sometimes heavy with cramps, I am a bit underweight, 5'3 100lbs, and I have skipped many meals the past month due to stress of college and my full schedule. Thank you so much! Also, not on any birth control or meds