Why Had Brown Discharge After Intercourse After Changing Birth Control Method?

Hi.. I am 24 years old and normal height/weight. I have been on birth control for about four years now and have had the same partner for 3 1/2. I recently ( 2 mos ago ) had to change my birth control method to the ortho evra patch due to changing my insurance. The first month I got my period when I was supposed to. This month, I should be getting in in the next day or so but here is my question: I had intercourse with my s/o on Saturday and afterwards I went to the bathroom and when I wiped I noticed there was what looked like brown blood or discharge. There was none on him and it went away right after that. Also, for some reason right after I just had this weird feeling that I was pregnant. I know the chances are very slim as I have been on birth control and take it as prescribed but is it possible? Would the dark brown blood/discharge be a sign? Thanks!