Sterilization and birth control

This is my first post but I need insight because I'm so unsure and lost. Long post. More to it but I don't want to pour my entire soul out.

I've had an iud appointment twice now and each time I left crying without the procedure being done. It scares me. With the stories of them moving and getting lost I just can't bring myself to get it done. My fiance and I already have 3 wonderful kids and I know we aren't Gung ho to have a 4th so I know that some form of bc has to be in place however it scares me. So yesterday on my way to the appointment I called my mom hoping to get some support and instead she told me it was a horrible decision, recanted stories she's heard and told me to just get my tubes tied. So freaking out I went to this appointment and immediately started crying. I feel like a pansy why can't I just do this. Doctor (who delivered 2 of my kids) tells me he's moving and it's his last day. More tears. Tells me they aren't going to do the procedure due to unprotected sex(notbsupposed to happen 2 weeks before appointment.. forgot and had frisky business 10 days ago) and I bring up tubal and more tears. New Doctor says no she will not do the surgery because of my reaction. Suggests fiance gets snipped. More tears. The thought of never having the opportunity to be pregnant again is shattering. Idk I'm probably being dumb but it's a huge thing. Anyways.. fiance is more than willing to get snipped and explains that he will never have another child and tells me if I want another down the road he suggests I find some guy and have a baby so that guy can raise the kid because he is done. What the..... now I'm silent and he gets irritated with me for shutting down. Ends up in a heated discussion about how we don't have enough intimacy and that because of his past he needs the intimacy and because we don't he doesn't think I love him. More tears. Idk 7 cups. Maybe I'm just overly emotional.