Could I be pregnant?

I had sex February 13 (Withdrawl method, but we don't know if it got inside at all, we had a little mishap lol). and was supposed to expect my period on the 21st of feb. On the 22nd I got this brown mucus, it wasn't enough to go on my underwear, it was only there if you stuck your finger in (tmi, I know!) anyways I was supposed to expect my period yesterday, which would've been day 28. Could I be pregnant? 
​I've felt a lot of "twinges" in my left ovary area, headaches, sometimes I'll wake up in the mornin and feel a little nauseated but nothin like I'm going to throw up, gassy, really bad acne on my chest/back(I normally have one or too, but now I have like a million!), I've been craving meat&soup a lot (weird for me) have to pee more than I used to 
​Oh and I'm 21 years old.