I think it's great that your fiance has you. Coming to this forum shows and says a lot about you. Lots of people don't take the time to try to understand they just get mad or run for the hills!
I was planning a wedding for a while, we postponed due to heath and money troubles, and I know first hand how stressful it can be on both parties and their relationship. I'm a forum type person so I found a wedding forum and found out I wasn't alone in how stressed I was...I know this doesn't help right this second, but maybe things will start to look up after the wedding. That sounds bad because weddings are supposed to be such happy events, and they are, but boy does the planning cause stress!
Like serafina said, you need to take care of you too. Don't feel guilty about needing support or if you need time alone or time with friends. You have so much going on right now with the job situation, the wedding, and now your fiance's bipolar acting up. Hopefully the psych will make changes if needed and soon your fiance will start feeling better. I don't think anyone here is going to give you trouble for how you're feeling. *hugs*
Bipolar, panic disorder, PTSD, PCOS, hashimoto's disease/hypothyroidism, and in the process of being diagnosed with crohns. Too many meds to list!