miscarried second baby

Kat
I found out I was pregnant early december, got an early Christmas present. Felt nervous bc we mc on june '16. (No kids yet!)
My numbers were very low at first and then starting jumping up, got to see the baby dec 26 and could see its heartbeat. Came to the dr two weeks later and no heart. Just got my dc this morning...
Im really sad but most of all worried... what is happening inside me that doesnt keep the babies. Can you share your success stories!?