How To Confirm A Real Pregnancy And A Molar Pregnancy ?

Hai , i am 28 years old, I had PCOD problem . So that i was taking treatment to conceive , In the 4th cycle i was pregnant . I went for ultra sound at 7th week doctor told me it shows 2 sac may be multiple pregnancy but no heart beat so you come to next week . The week doctor told me it may be molar pregnancy. after that i had a DNC (aug 26th 2011)... after that am taking regular HCG test and scan. My Utreus , and endometrium thickness was normal. oct 1st My HCG level was 1.2.In november i had a missed period .i had taken a pregnancy test .the result was Positive , i was bleed (one drop) on 50th day (Nov 27th) . I went for a ultra sound scan . It shows nothing . That time MY HCG is 3000. next week( Dec 6 ) HCG is 64 . this time i had a sever abdomen pain . a small tissue like a sac 2.5 inch came out with my bleeding . Whether it is molar pregnancy or pregnancy or not ? after 28 days my next period is came (Dec 25th ) My Question is When i try to conceive ? Now My HCG level is zero