Pregnant after miscarriage.

Good Afternoon,

This is the first time that I have posted anything so I hope I am putting this in the right place. I am hoping that someone can help or offer a little bit insight into things that are going on with me. I have had 4 miscarriages in 12 months. I have had a successful pregnancy. I had all the tests done after the second loss, consequently, I am now on megafol, progesterone, oroxine and using clexane once I have a BFP. My question really revolves around what is happening with my cycle. After ovulation has been detected then I experience spotting for approximately 10 days before my actual period. In some way I feel that there is a relationship between the spotting and the fact that I cannot carry past about 7 weeks although my specialist says that is not the case. By the way, this is the second specialist that I have seen and I feel that he is doing a lot more than my previous one. Also my cycle used to be 28 days on the dot and now, for some reason it has changed to a 21 day cycle for the last 18 months. Sorry if it seems like I am rambling but I am so confused. I have no trouble conceiving just carrying. Has anything like this happened to anyone else and, if so, what did you do to achieve a successful full term pregnancy.