<human>: Can you condense the text into three sentences or less?

Throwaway for obvious reasons.

I've been with my fiancé for almost 6 years. We've lived together for a little over 2 years. On paper, he's an amazing fiancé. He worries about me, and he tries. 

However, he's extremely boring. There's a lot of times he doesn't want to go out because he's tired (meanwhile, I worked 2 jobs and went to school fulltime). He doesn't want to go the gym with me because he "doesn't see why he needs to." He also doesn't know how to communicate with me - so if something is bothering him, or if he does something that bothers me and I communicate it to him, he shuts me out. I think he is bipolar, and he admits that he thinks he is as well. But he doesn't see why he needs to talk to someone. 

Lately, I've been traveling a lot to Boston for work, and I've noticed that my eyes wander more times than not. I would never imagine cheating on my fiancé, but I honestly don't know what more I can do. I've suggested counseling, therapy, anything I can do to strengthen our relationship. Our sex life isn't lacking, but it's become routine to the point where I don't look forward to it any more. It's more or less what I do to make sure he's happy.

I love him. I truly do. He has a great heart, and I know he's seriously troubled in his mind. He's never had a positive influence in his life, and I know I'm not responsible for that. I'm just not sure of what to do because I know if we were to break up, he'd be broken. I don't want him hurt, at all.

We haven't set a date yet, but everyone in our family is so excited about us getting married, and his brother is offering to pay for a lot of it. I feel like I'm in such a whirlwind and I'm not sure where to go from here.

Sorry for the rambling. I haven't slept much in a few days.
<bot>: I'm afraid of being my fiancé's crutch for the rest of my life, and missing out on life itself, but I love him so much and I don't want to make any hasty decisions or hurt him.