Should I be thinking of having a baby or getting a divorce or non?

My husband and I are married for 3 years now. And have been in a relashion ship before that for 12 years. I've been wanting so bad since the very first day of our marriage to get pregnant and have a healthy baby. We tried so hard and nothing seemed to work. the whole process of trying every month seemed like and endless emotional roller coaster to me. I cried allot every time I got my period. and felt more and more devastated and depressed. It hurts so bad. every time I see a pregnant woman or hear that a friend or a relative is pregnant or even see parent with their children I cry and feel burnt from the inside. I became isolated. This thing got me so depressed. My husband and I finally decided to go for IVF.

I sold my car so that we can pay for the IVF treatment and started with the protocol and taking the medications. and just when I did I found out that my husband is snorting heroin again and this is his 4th time of relaps in a year. It was like spilling acid on an unhealed wound. I felt like the whole world's doors are shut away from me. I grieved but decided to postpone the IVF treatment and stop the medications. My husband promised to stop but never did. I begged him to get into a rehab center but he refused saying that he can quit when he wants to without the need of a rehab. I tried everything with him but nothing seemed to work with him. I also went to see a phsycologist and even the phsycologist agreed that there is no way out of this except a rehab center outside of our home country. My husband finally agreed to get a professional help but he didnt agree on a rehab and does not want to leave the country for a short period of time. I'm starting to loose hope in him and think that maybe its better if I leave him but yet again I know if I did then I would get his situation to even worsen.

I love him but dont know what to do? Some say that maybe if I do get pregnant and have a kid then he will change and feel more responsible but I dont know if that would work or if I should even risk chancing something like this? I want a child so bad though and I just sit everyday crying for hours just wishing I had a child.. Should I listen to my instincts and proceed with IVF or should I wait until my husband sobers up or should I think of a divorce? Has anyone been through this or know anyone who's been through the same thing? could it be that the joy of a having a baby will make my husband be a more responsible person and takes a whole new step ad positive action into changing himself into a better person?? not that he's a bad person now, he's a very loving husband and treats me so well but I really dont know why he go himself into what he's in in the first place?

Additional Details
both of us been tested for all STD's and STI's after all its an IVF protocol to be tested befor going for IVF. My husband does not use needles he just smokes and snorts heroin