Could I Be Pregnant? Need advice!

My last period was on August 25 but it was really irregular because before that my period was pretty regular and was on July 17. I had sex with my boyfriend on September 1st and it was *unprotected*, he came inside me and I’m not sure when I ovulated but I know before I had my second child I always ovulated on the first of every month. I conceived my last baby on May 1, 2017, she is now 8 months old. Anyways, the thing is I was suppose to get my period two days ago so it’s late and I am noticing brown discharge, it’s only there when I wipe and at first it was pink but now it’s brown and pretty much gone 100%. I thought it was my period but it isn’t, about two weeks ago the exact same thing happened so I am sort of freaking out. Has anyone experienced this? Could this be pregnancy because we weren’t planning this, I don’t know what I’ll do if I actually am.

I’m not birth control.