I lost my baby..............?

I am ttc for more than 3 and half years.I got pregnant with my first IUI .Initially the doctors scared me that my hcg levels were low and then all of a sudden I was told everything was OK but then I lost my baby at 13 weeks since the bladder for the baby did not develop properly.After my D&C we tried another six IUI' s but to no avail.After that we started with IVF and once again I got pregnant on the first try but unfortunately my hcg levels dropped again and we lost the baby again.My question is I am able to get pregnant but because of this hcg levels I am losing my baby.Can this be rectified?I am meeting the doc this Saturday but I just want to know beforehand whether anyone faced the same situation and how did it get resolved?