I think im having a miscarriage. im not due for my period for two weeks.?

i started having cramps and spotting last week and i thought that was odd and might be pregnant even tho i'm not due for my period for two and a half weeks. monday i woke up and i was bleeding. cramping started and by 3 pm the bleeding was very heavy with clotting. the cramps were so bad i couldn't even stand. i went to the er, they did a urine pregnancy test and i came up negative. i ended up leaving because i waited for 5 hours and still wasn't seen by a doctor. i saw my gyn in the morning and he sent me for an ultrasound, it was normal. Yesterday the cramping and bleeding was very heavy and painful. i see the doctor again tomorrow. my question is, was it too early for the urine to show pregnancy? was it too late for the ultrasound to show it? and am i having a miscarriage this early?