I just can't win.

My fiancé and I have been together for 6 years. In the beginning of our relationship, he worked a crazy schedule. I never knew when I'd see him and neither did he. Finding time for each other and maintaining our own lives was a real challenge. Most of our time together was spent while he was working (after I got off work). Eventually he changed careers and has a "normal" job schedule. Home every night and most weekends off. Things were perfect. We go on spontaneous trips. Have dinner together every night. Go out on the weekends. It's a total life changer. He recently mentioned becoming a volunteer firefighter for a different town with his buddies. We discussed it and I told him several reasons why I didn't like the idea (Health reasons, time management reasons, risk reasons, etc...). He didn't like my response which turned I to an argument and he joined anyway. We continued arguing about this for weeks. He barely spent anytime at home and I was fuming with anger. I started noticing him hiding his phone from me and getting angry if I touched it. Red flag! I've never been one to "check up on him" but my insecurities led me to do just that. I found out he was totally bashing me to one of his buddies (a female) that he worked with in the past and who is a volunteer firefighter with him now. Calling me all kinds of names and saying I don't do anything to take care of the house and I think I'm better than him etc. Then he began complementing her body and asking her to find him a new girl like her and that he was over my crap and was looking for a rental house to move into. We of course got into a huge fight over it and I told him I couldn't trust him. If he was that quick to run to another woman and bash me and flirt with her, how can I? A few weeks went by and we had another chat. I expressed all my emotions and we finally came to an understanding. He apologized and said he wants to fix things and I'm willing to try. Now let's get back to the firefighting. He works his normal job all week and wants to volunteer on the weekends. I am very grateful for firefighters so don't get me wrong when I say this, but where do I fit into that schedule? I asked for a compromise and he tells me to come up to the firehouse. Yeah the same place I don't want him at and the same place the woman he vented to/flirted with is at. Seriously!?! I don't see how I can be happy with all this. Any advice would help. Am I being selfish?