I have read this same problem from so many of our members with every kind of mental health problem and it is sad but so true that others do not understand how we feel.
I am lucky to have a supportive family but my husband has had his moments and so have my children to the point that I felt guilty and all alone but in the end my husband is my support person even thow he will waver a bit.
If your fiancee' is not dealing with this it may be wise to step back a bit and do work through your therapy and then talk with him more. I know what it is like to feel all alone and to be told to "get a grip".
In a relationship such as marriage it is for better or worse and running away when things get tough is not a trait you need in the person you plan to spend the rest of your life with.
Perhaps with time he will learn to understand your disorder better which would be wonderful but now he appears to be taking it personally. Please do not take on responsibility for his feelings. You are two people each responsible for your own feelings.
Don't give up but do reach out for the help you need.