Implantation bleeding, miscarriage or simply weird period timing ?

My period was supposed to start on the 29th of last month but it came on the 3rd of this month and after the first day of heavy bleeding, it slowed down yesterday and now it's all gone so it just lasted about 1.5 days. My cramps started from the 26th of last month and never healed.... I've been to my internal medicine doctor and gynecologist but all the reports came as normal and negative for pregnancy test. My doctor asked me to come back after a week if my condition doesn't get better. But could it be that this was due to implantation bleeding and the blood test couldn't catch the pregnancy hormone sooner? or could it be miscarriage ? But I'm not sure if the traces of hcg goes away so quick after miscarriages. Gosh this is so weird, my period would normally last for 5-7 days....I know I can wait and check with my doctor in a week but don't have much patience. Also, could it just be birth control pill withdrawal symptom? I stopped my pills in the middle of September. Anyone here experienced anything similar ?