second miscarriage in a row.....why???

After going through a miscarriage earlier this summer. My husbans and I were thrilled to learn after deciding to try again six months later we were pregnant again immediately. 
We miscarried early on the first time. 5w6d to be exact is when I started cramping and bleeding. So in my head that was my marker just gotta make it past that and I'll feel better. So the morning of the 5w6d I got up and noticed first that my boobs weren't as heavy or sore as they were the previous day. Went to the bathroom and when I wiped there was two spots of blood. I knew immediately. Like Deja Vu. Sure enough by the end of the day yesterday I'm bleeding full force like a heavy crampy period. 😰😰😰😰😰😰
Another one lost the exact same way. The exact same gestation to the day. What does that mean??????? And why?????
Doctor wants to do an ultrasound. I don't see the point. Been there done that. I already know. 
I'm more interested in why. Am I sick?  Cancer? Hormone imbalance? Infection?  Can I check for these things???
I do have three healthy boys from two all natural pregnancies. I know I'm blessed. And I'm so grateful for them. But we have one more to complete our clan. We were hoping for a baby girl to complete us. And now I'm wondering if I'm being greedy and God is trying to tell me to be content with my guys. 
My heart goes out to all the women that have gone thru this repeatedly. I don't think I have it in me to do it again. 
Anyone else have similar miscarriages and found out why and then went on to have normal healthy pregnancies and babies????