Hi there! First of all sorry for your losses. I know exactly how you feel
To make you feel better THERE IS a HOPE. I have heard stories of women that have had 2-3 pregnancies before they discover they had an uterine septum, I have heard stories of women that have been able to keep a pregnancy after several miscarriages without going for the uterine resection surgery and some women soon after the corrective surgery got pregnant and keep the pregnancy. What to mention that there are women, who did the corrective surgery and they still miscarry and the question is why women with normal uterus still miscarry?.
I belive with septoplasty improve the chances of the outcome of the pregnancy further on, by having more space in the uterus for the baby to grow, but not the risk of miscarriage, since with every miscarriage there must be a different reason why it happen( could be because of the embryo, hormonal, bad egg, shorter lutheal phase,etc).I guess regardless of septum the risk of a pregnancy to miscarry is the same with the risk of miscarriage having a normal uterus.
Another thing, To make you feel better the septum does not grow back. Usually after a month of so after the surgery the septum retracts back and that is called a residual septum which basically it is just a remained tissue from the old septum. The septum is very stretchy just like a wrist band and when the doctor cuts it the septum snaps back, Some doctors suggests to go for a second procedure some say it is not the case to go back since after the surgery the endometrium is not the same and may reduce the chances of implantation on the septum site and therefore the embrio won't implant in that spot.
Did you had a second Hysteroscopy or a SHG/HSG to take a second look at the residual septum and see your uterus appearance? If not I advice you to have one just to make sure the everything looks good. I tried to send you a perosnal email but I don;t know why isn't working. Feel free to send me a personal message. I personally met women that now are mothers and have had septum.
Hope I helped.