Help!

Okay so guys I've been freaking out, and I will warn you this is all way to much tmi and a lot of info.  I am on birth control but I'm one of those people that always use double protection. So on my 11 day of my cycle it said I was fertile me and my boyfriend were messing around and didn't use protection. I wouldn't be really worried of or was just that but he pulled out but didn't go far enough and it got on me I wiped it off as soon as I could. Then on cycle day 19 we had had sex the day before but I had cramps and back pain, I could have been making it up in my head thinking I was pregnant but I'm not sure. This whole cycle I have been very very stressed with starting off two new jobs and getting my car fixed and just a lot of things. So today is cycle say 27 and yesterday I had woken up had a sharp pain and then I had some brown, I'm not suppose to start until Wednesday so I'm not sure of it's spotting or my period I had some more this morning. I never start early on birth control but with this much stress it could have messed me up. So guys what I'm asking is do you think I could be pregnant and it's implantation bleeding, spotting, or an early period? Thank you so much and I'm sorry it's long.