very sorry to hear about your struggle anon. you have my sympathies..mad props for sticking it out, not giving up all these years.
i really don't know what you've tried already so i can only give you the most general advice. And of course It would help to know more specifically what kind of mental illnesses/issues your dealing with.
Are you really sure if you have explored the limits of your healthcare options?
if not, a social worker could help you find out, and you should be able to see one for free at your county office (Im assuming you live in the U.S.)
do you exercise?
Regular exercise, especially cardio, and especially doing it outside in nature, can work as well as some medical drugs for your mood and outlook. and don't think you have to go all out to get the benefits. if youre not psyched about sweating hard, even light cardio done consistently has some really positive effects.
how is your sleep?
do you get enough and do you feel rested after? that is probably even more important than the exercise.
Do you allow yourself "chill time" to just kick back and enjoy yourself?
Hedonism and sloth are vices, but some people swing the opposite way and just don't know how to relax and really enjoy the moment, because they are always busy, running a race to nowhere on a treadmill. Get out on a regular basis and indulge in something you really enjoy doing, just for the sheer pleasure of doing it.
Lastly, Im not the type to go for feel-good, airy platitudes, but there is this very short, adorable, illustrated book i read called The Meaning of Life that was a charming gem. https://www.amazon.com/s/ref=nb_sb_ss_i_7_19?url=search-alias%3Daps&field-keywords=the+meaning+of+life+bradley+trevor+greive
Whatever course you decide to take, you're right about something: you should ponder it soberly to avoid rash decisions and decide based on a solid foundation of reason.
Im rooting for you anon. May the best come to you.