Recurring miscarriage

Has anyone had multiple miscarriages and found out a reason for them? I'm on my third one and feel like there has to be an issue. I had one in February at 12 weeks (baby only measured 8), then one in June which was classified as a chemical. And now I'm going through another at 6 weeks, my HCG started slowing down in rising and now it's going down. I feel like there has to be a problem. This can't be normal or just "bad luck". I'm starting to feel hopeless and like it's never going to work. Please give me hope. Thank you!