Oy Vey! I just caught up on this thread. First of all I am so sorry that you are going through all this. I think to some extent everyone goes through rough patches. It all comes down to whether or not it is worth it to you to work through the problems.
I think what is going on here is that you each have stuff that is bothering you and planning a wedding only adds stress to the situation.
Like Jessica I am a complete neat freak. It almost causes me anxiety when I see my home in disarray. My DH is a total slob. We constantly fight about this. Unlike Jessica however I did feel trapped. Not to the point where I wouldn't marry James over it but it was a source of discontention. It really stressed me out to constantly live in a pigstye (sp?) We also had financial issues (namely James was a huge spender and mismanaged his money all the time). There were times where I got cold feet and I wondered if this was really what I wanted. Not b/c I didn't love him, but just b/c I didn't know whether I was willing to live my life like this forever.
That being said I never walked out on James and I never threatened to either. I knew that marriage was hardwork and you can't just give up on someone or disrespect them. When the going gets tough in a marriage is the time when you have to be there the most for a person not just give up.
I've only been married for less than a week so clearly I'm no expert. But I can tell you that days after the wedding I instantly felt better b/c all the wedding stress was gone. And I was able to use the money we got from gifts to pay off a lot of his debt which instantly relieved a lot of our stress. Even better we talked about how we are going to work together and change things around...these are the positive talks that you and your FI need.
Also, James realized how important it is for me to have an organized home and when I went back to work I came home to a sparkling home. He cleaned the entire thing for me to make me happy. Its the compromises that will help build your relationship and make you guys stronger as a couple.
I think right now its important that you both talk about what is important to each of you in life. Tell him that you love him and you want him to feel the best he can about himself and that is why you want him to see a therapist and take his pills. Threats and nagging don't usually work well in a relationship. He has to want to do it. If he's not willing to get some help then it is ultimately up to you to decide what to do with that piece of information.
However I do think some of your problems are fixable. Once you start losing more weight you will feel good about yourself, your sexual relationship will improve and he will be happier as well. If you take some time to clean your home a little more it might improve his mental health as well. Talk to his family and see if you can get them to back off on him a little. Explain to them that this is stressing him out. Log onto BDW and talk away about all your wedding plans. Choose which convos about the wedding to have with him (e.g. money and payments) and save the miniscule details for us girls on here who love to hear about it.
I really hope you guys can work this out.
Sorry this was so long, but I just wanted to give it the attention it deserves.