Cramps & light brownish discharge ?

Okay , so yesterday I checked my underwear it's was brown , I started cramping this morning & I used the bathroom and I wiped it was brown clearish , I had to go to the hospital for a allergic reaction , and they made me do a urine sample , my uti & pregnancy came out negative , I'm also on the pill but missed it last weekend and had unprotected sex , was it to early for my pregnancy to be detected & am I possibly pregnant ?