Since your test now says negative, chances are that you aren't. Are you sure the positive you saw wasn't a false positive, for eg., did you look at the test after the stipulated time had expired? bleeding for three days sounds like a normal period. Did you notice any excessive bleeding this time? if your period was as usual, then that could be an indicator of a normal period and not a miscarriage.
Doing a blood test to settle it once and for all may be a good idea. wish you the best!