Sounds like you lost track of why you set off in that direction in the first place.
I'm sure you were fully aware of all the hard work and financial investment that was ahead of you when you took the plunge. Something inside you told you that it would be worth it. You were ready and willing to dedicate years of your life to a goal. By your initial post, I'm understanding that at times you even felt motivated. Right in the middle of hardship and adversity, you soldiered on and, on some level, you felt good about what you were doing. That feeling is available to you. You just need to understand it enough to be able to work towards it whenever you feel like you've lost it.
Did you start playing music to compare yourself to others? You feel sub-par compared to others? By that reasoning there should only be one bass player in the entire world. The best one. All others are inept. Not a very viable outlook, is it? May I instead suggest comparing yourself to yourself? Don't try to be as good or better than others, try to be better than you were yesterday, or last year. Do learn from others, use them as inspiration or whatever you want, but don't use them as a way of detaching yourself from your own position and belittling everything you've accomplished. Don't look down, look up. The view is much better.
So what did you start down the musical path for? For me, I discovered I loved music. It was this one guy came to our high school to do a show for some cultural thing or some other. I lived in a very remote and isolated village in northern Canada so seeing someone properly play an electric guitar on a somewhat professional level was rare. It wasn't even a type of music I liked at the time, but when I saw someone playing an electric guitar for the first time my brain exploded. I HAD to do that. The idea of using an instrument to make sounds in a musical way gave me the shakes. I was obsessed. For the privilege of playing music I've driven countless hours for little to no pay. I've been belittled, criticized, mocked and misunderstood. I've been poor, cold and hungry. I've stood in rain, snow, swarms of insects, scorching heat, dangerous neighbourhoods. No matter how many times or how hard I hit the bottom, I can't help myself; I love music. It's insane, but I love it. It's just sounds that evoke emotions, feelings and memories but it gets under my skin and I have to have it. Listening isn't enough, I have to be a part of it. But that's just me. You have your own motivation. When you find it, I guarantee your current problems won't even show up on your radar. Find that first feeling that made you go insane and choose a ridiculous path. Don't forget to enjoy the ride and help others.
P.S.:
I'm not going to pretend I understand bipolarity other than it involves mood swings. Please understand that I don't consider my opinion to invalidate what you're going through. If bipolarity makes things harder in the end then I'm sorry you have to deal with that. It concerns me a little that you made an offhand reference to suicide. I hope it was only an exaggeration. If not, then all I can say to that is that I've been that low and the only way I got out was to be proactive about changing my own mindset rather than hoping my environment will change. Ironically, that ended up changing the environment I live in for the better. I really hope that helps. I've never met you, and perhaps I never will, but I still care about what happens to you. I want everyone to enjoy what they do. I'm always willing to help someone make sense of things. Just say the word.