Miscarriages

I'm 33, and my husband and I have been ttc since August of 2015. In November I got my first bfp, only to find out within days that I was micarrying. Disappointing, of course, but we jumped right back on the horse and started trying again as soon as I got my first AF after the m/c. Got my 2nd bfp in February! First visit to the doctor at around 5 weeks showed my HCG was good and my progesterone was ok, but a little on the low side, so I was prescribed progesterone pills. Then right at 6 weeks I started spotting. :( Went in for bloodwork and an u/s immediately, which the u/s showed nothing, and HCG had only doubled within 6 days.... I was told I was miscarrying again. I am heartbroken. I'm going in for testing to see if there is a medical reason for my m/cs. I'm anxious to get started and ttc again, but I can't help but feel worried and scared. Greatly in need of some success stories, and any advice you may have.