Birth control

Lisa.
I had came in to planned parenthood 3 weeks ago. I have been taking birth control pills ever since and I've been taking it every day. I take it at the same time except for one day where I was late 10 mins but other than that I am always on time.  I had sex and semen had gotten into me thinking that I was protected because I have not skipped a day and usually take it on time except that one time that was 10 mins late and ever since then I've been spotting brown. I have been spotting for 3 days now which was right after intercourse. I don't know whats going on with my body and I am very worried. Please help me I don't know who to talk to. I had intercourse jan 10th & I took my pill 10 mins late jam 13 & ever since then I've been bleeding brown & as of right now when I wipe when I pee it's red. I don't pee blood but there was once a large blood string come out. PLEASE HELP.