Miscarriage at first IvF Cycle

I'm still upset and feel sooo sad as I thought my rainbow baby lost few days ago at 6 weeks. I just confirmed it through blood work which falls at 56 from 498. Dr instructed to stop all my medications and let my period begins. I am planning to do another embryos transfer next cycle. I don't feel right as I have high hopes that it will stick around just like other women in my clinic. So envy seeing them visiting the clinic for their first ultrasound and to hear their baby's heartbeat. I hope I can figure it out what did I do wrong why I did miscarriage. Feel so hopeless and I hope I can get the answer my next fertility visit. Could it be my progesterone, thyroid, chromosomal abnormalities, just too many to consider for the possibilities. Now I am worried it will happen again in my next transfer. It's totally a nerve wrecking experience but obviously I will never give up!