Multiple miscarriage - need hope!

My husband and I have been married for 2 years. We started trying to conceive in April. In May we got a BFP, however days later started bleeding...concluding a chemical pregnancy. We started trying again and in June got another BFP, the doctor tracked my HCG however found it wasn't rising and soon after I miscarried again. The last one was in September we got another BFP, the doctor tested my HCG and gave me progesterone suppositories, however after multiple blood tests found the HCG was rising but not doubling, which resulted in miscarriage.

We seem to have no problem getting pregnant, but rather staying pregnant. My OB doesn't seem to concerned yet, however to us, it feels like the end of the world. Any suggestions, stories, encouragement?! Thanks! 💗