I Had Sex With My Boyfriend 11 Days Ago And

I had sex with my boyfriend 11 days ago and the condom came off when he pulled out, after he ejaculated inside me. I took postinor 2 within the next 12 hours. This occurred in the middle of my cycle (so during my 'fertile period') so you can see why I'm really worried. It is now day 25 of my cycle and I have (a lot of) brown clumpy discharge (itching on the exterior of my vagina), and a little cramping with tender breasts. However I usually get tender breasts a week before my period is due. I am really worried that it might be implantation bleeding and I might be pregnant. I should also mention I had a UTI last week. Could this be a bacterial infection or IB?