Is it my period or random bleeding?

I had “unprotected” sex (I’m on nexplanon that expires this coming August so technically not unprotected, but he came inside of me which is not the reg. for us) this last Tuesday and then started bleeding the next morning. It would be what I consider an EXTREMELY light period (regular tampon every 8 hours) for about 4 days, and then spotting the fifth. Normally, my periods last 1-2 weeks and are extremely heavy with a ton of PMS, and then I got this? I can’t say it was out of the norm because I don’t have a “norm” on nexplanon, but I am curious on if this has anything to do with the sex from the previous day or if I should be concerned? (I know, see my dr... just curious on your guys’ input first!)