Faint line

So i took a test Thursday may 18th and it came back one faint line and another very clear dark line but the day before it came back negative then the day after it came back positive and the day after that negative and when i went to the doctor he said my hcg level was low it was a 4 something and during all of this i was spotting extremly light red and then after the third negative it started to be a heavy red and all the doctors could say was that i was on my period please can someone explain