So this is a long story, bear with me

I found out I have a cyst on my sacroiliac joint that is causing my a lot of pain. I can hardly sit at all. My ortho says I need surgery BUT he suggested I wait until after I have children to have the surgery. He says this is because the act of child birth will essentially ruin any join fusing that takes place. 

I am only 8 months post-op, and I was told I was supposed to wait 18 months. I am having this conundrum. Try to get pregnant now? or still wait and live in pain? I want to have 2 children, which means I will be in this pain for a minimum of 2.5 years. I dont know if I can do that. 

I also am afraid to get pregnant and ruin my sleeve. I am still about 40 pounds more than I want to be, and i fear that if I get pregnant now, I will never reach my goal. 

So here is my question to you all. Is it possible to still lose weight after pregnancy with your sleeve? or does a pregnancy stretch out your sleeve and basically ruin everything the surgery did? 

Thank you!