Hi everyone, I was just wondering if anyone could give me a little insight into my situation.

I've been on birth control for my for a few years now and recently went on antibiotics. I was told by the Doctor how the antibiotics could interfere with my birth control, so my boyfriend and I refrained from having intercourse (we haven't gotten to that point yet anyway so it didn't bother us) while taking the antibiotics but still did outercourse. Well a little over a week ago we were grinding and he didn't have any underwear on but I did, and when we were through i realized there was a decent amount of precum on my underwear and thighs and I was concerned that some of it may have gotten on my vulva, which I have been told, although unlikely can still get you pregnant. To put my mind at ease I took Plan B about 50 hours later (Doctor told me my antibiotics wouldn't affect the Plan B so I've continued to take them). I stopped taking my birth control pills a few days later as it was my placebo week to get my period and now I'm almost ready to start up my pills again and still haven't gotten my period. Could I be pregnant? Or is did the Plan B/Antibiotics just mess up my cycle? I have been experiencing severe cramping, swollen and tender breasts, with back pain and loss of appetite (which I don't usually experience during my period due to the birth control I take.)

Any ideas as to whats up? If I am pregnant how long should I wait before taking a pregnancy test?