Can you begin spotting because of stress or start a period early because of stress?

About two days ago i recently found out my boyfriend was cheating on me and it caused a big surprise and I was very upset and hurt. Well today when i went into the bathroom there is blood on my panties my period for this month is supposed to start towards the end of the month. We had unprotected sex last month but my ovulation date was yesterday it looks somewhat like period blood its very red and there are clots. I just want to make sure im not pregnant with a cheaters child. i am taking the pill as well