Should i or should i not

Anita
Ok I need some advice....I got on the shot on Feb 18 and my husband and I had unprotected sex that same day and now I'm 4 days late...idk if I'm just being paranoid or if its possible that I am or that my body is trying to get use to the BC. I haven't been on the shot since 2008...Is there a chance I can be pregnant???