Second loss started this morning :( what's wrong with me?

So I had a chemical in December and finally fell pregnant again! I was 6 weeks exactly and just got this feeling last night that I was miscarrying. I went to bed and woke up and my symptoms were gone. I took a test and while I was going to the bathroom noticed bleeding. The test was almost negative. My doctor and I are almost certain it's happening. I just want to know what's wrong with me?! As I was walking in to get my blood drawn there was a very young couple (15-16 years old) walking out with their first ultrasound pictures. I'm married and 27.....both good jobs and educated. Why can't we have a kid?!