"You never regret having a baby. You will always regret not having one." Yikes - that's got to be one of the most untrue statements I've heard. First, the words "never" and "always" are dangerous words - fighting words, in fact. You should have learned that in therapy by now. Second, you must know realistically that there are folks that regret having another child, or a child at all? Just because it isn't "mainstream knowledge," surely you must know that folks can regret just about anything at all - including kids?
I think that you need to spend more time in grief counseling, not marriage counseling. It seems as though you have fixated on the fact that you maybe initially were not happy about the pregnancy, thereby somehow causing the miscarriage. This is common to feel this way, but without addressing it, you will always seek that "replacement pregnancy" to fill that guilt. Even going so far as to destroy your marriage to do so.
You know that you could force your husband to agree to a 3rd child and still find out that your childbearing years are over for whatever reason. Or have another miscarriage.
If prior to this, your life was good, your marriage was strong and you were ok with having two kids, then I think it is time to focus on trying to get back to that, rather than focusing on forcing your marriage to a place it clearly cannot survive.
Good luck - as a mom who suffered multiple miscarriages, which ultimately lead to a hysterectomy, I understand the drive and fear behind what is going on . . . I really do.