Sterilisation and positive test

I was sterlised a year ago im due in any day now, the last 3 days I've been spotting brown blood ive took 5 test 3 looked like there could have been a vv faint line they were cheapie, i did 2 first response one in the morning looked pretty negative, did another on yesterday evening and there's a faint pink line what are the chances of this being accurate? What could the brown blood be? Tia