Smoking cause for infertility?

Jeana • My boyfriend and I have lost babies and we really want to have one together. We have had three miscarriages and have lost four babies. We were pregnant with twins. Maybe this will help us.
Ok so for thirteen years I have tried to get pregnant, in those thirteen years I never once got a positive pregnancy test. In 2014 I quit smoking for a month and a half. I fell pregnant but lost my baby, I got pregnant a few months after that and lost that one, and month after I lost the second one I got pregnant again and lost twins.
I smoke now and it's a bad habit but I honestly don't know if really smoking is to blame. I feel so stupid and selfish but I've been smoking since I was twelve and I know it's not good. When I quit smoking I finally conceived, was this a coincidence or am I just going insane? I know plenty of women who smoked their whole life and we able to carry babies, those babies turned out just fine. Help me.