is it possible to have vaginal bleeding if pregnant?

I think I got my period this week, but it's only five days and considerably lighter compared to my usual seven days and medium to heavy flow. I have been exercising a lot (lacrosse and running) and definitely have been under a decent amount of emotional stress so maybe that impacted the duration and flow. Is it possible to be pregnant after intercourse but no ejaculation three weeks ago? I think I will test in a few days to be sure.