Miscarriage fears extremely anxious

Am 6 weeks and 6 days pregnant going by doctors workings out although since I keep track of Fertility etc I feel I am only 4 1/2 weeks. Anyway long story short, my hcg levels have been around a 3-5 week range hence drs concerns as she thinks im over 6 weeks so a transvaginal scan was ordered. The scan was done yesterday so no news until monday/tuesday but last night I had period pain symtoms pretty strong and this morning woke with same pains and now passing blood in the toilet bowl and after wiping, am now wearing a pad to monitor amount although atm no clots. How can I go from pregnant 4-6 weeks pregnant to period this morning with no obvious tissue passing? Really sore back and abdominal cramping :-( can anyone shed some light here. Still hopeful but am losing faith. Anyone else been through this and had a positive outcome? So sad depressed and lost.