Long story short I was on antibiotics and missing and had unprotected sex 4 days later. Under the suspicion of pregnancy I went off my birth control and received a clumpy, dark brown discharge on and off over 2 days, this was a week after conception if I stayed on the pill I would have been schedule to get my withdrawal bleeding the week after. I've heard withdrawal bleeds aren't true periods? Can I in fact be pregnant because the brown discharge was only old, dark brown blood? If so it has been 43 days since last period(almost 6 weeks) have felt nauseas but have not vomited only the feeling like I'm going to do, my nipples feel bruised when I touch them, I have to urinate regularly and often feels like small amounts of wee are leaking out of me but usually either urine or a drop or two of a white discharge. Has anyone had similar experiences?

I would hazard that some of this is caused by the illness you're on antibiotics for. The symptoms you're feeling are probably more due to a PMS response then pregnancy. The typical pregnancy symptoms don't set in until late first trimester. You're also hypersensitive to this because of what you're thinking and observing. What you would normal not pay attention to is at the top of your mind so you're more sensitive.

You said that
..you were on antibiotics and missing and..... What are you missing?