I don't understand bipolar - so I am unable to really unable to fully under stand what it your going through.
Here is what your doing right:
Your in school stick with it - don't take a semester off if it's to late to enroll in normal classes look into mini-terms and online class talk to an adviser and get some guidence on classes your really interested in but that fit into your degree plan. Your dealing with some shit I get that it's very hard to go back once your leave....your going to see success story's from people that take that semester off and come back....just assume your not that person and move your focus to taking a few classes your intrested in.
Asking for advice, not shelling up. Your a human not a turtle.
Working - even if your not making bank save the shit out of your money, don't go out or if you do make it a game to see how cheap you can do it...
What you might be doing wrong: I don't understand your illness and I am a pragmatist so this might seem harsh
Your 19 years old - way to young to tie your happiness to someone else you don't know what your going to want out of life this isn't the 1840's you have plenty of time so you got dumped - you will set the tone for your career and the rest of your life over the next 5-8 years and the happiness of your future family don't drop out and limit your chances.
Being your age is hard for just about everyone - it's not easy your going to lose many friends and make new ones.
Finally some personal info - I went to smallish university in Kansas I worked in the maintaince dept - I made shit and got the worst jobs I was the guy that had to go collect the change and restock tampon machines in the womans bathrooms and dorms - I had to wear a shirt with my name on it - so everyone knew my name and that I was the tampon and trash guy on campus. seriously.
Happy Ending and what you have to look forward to: I went form being a tampon change retriever / campus trash collector to a guy that has been married 9 years and at this point I make an embarssing amount of money in my career. I have a pretty awesome dog and an amazing wife wife a great career....
Hang in there deal with your illness DEAL with it don't let it be an excuse or crutch or limit your education or success.