Hi, my last period was on 1/3 and missed my period this month. Had intercourse on 16/3, withdrawal method, on 18/3 i had spotting with pinkish and brownish for 4 days. Did a pregnancy test 2 days before and its negative. Did an ultrasound today with thick uterus images. Any chances of pregnancy? Had cramping, bloated and back pain since i missed my period day 1.