That feeling you talk about like you are totally disconnected from everything is the worst. I used to sit looking at my gf and it was like I didn't even know who she was or if she was my girlfriend, man I even felt that way towards my own family like I'd never known them. The whole world felt so fake and I made the mistake of googling it and my obseesive thinking started there. My thoughts ranging from weird to damn right disgusting and frightening. It made me doubt even the most natural things about myself, like I used to ask myself how do I know that I like the clothes I wear what if I'm not really this person? How stupid is that but it caused me massive anxiety! I used to take some comfort from the fact that I knew how I felt before and nothing had changed other than the fact is stopped smoking, I mean you don't just wake up one day and stop loving the things you loved for no reason right? I'm glad you've spoken to your fiancé, hopefully she can support you in the way you need, what's important is you realise this is within yourself and when times of irritability come don't take it out on her, just say to her you need to take a time out and go meditate or do something relaxing for 20 minutes whilst you refocus. You'll be ok man trust me, I thought I'd never be where I am now and low and behold I'm here trying to help others. It's kind of reassuring to me as well knowing that somebody else is having similar thoughts as to what I have been through, I know how hard I searched for someone else who was having the same sort of thought processes but i could never find the answers I craved so badly. Hopefully I have saved you some suffering bro.