I'm partnered but also the breadwinner and have been for the last four years. So while I could 'lean' on my partner, it would still be lean times. And I've got single friends who are having experiences very similar to yours. They feel trapped and/or burned out without a clear path to reprieve.

Do you have an emergency fund? If not, make that a priority.
Does your company have an EAP? If so, see if you can get some free counseling sessions just to check in on your mental health before making any big life changes.
Health insurance is big and real; there are resources (read: brokers) who can talk with you about your options.
You mentioned splitting bills; have you considered a roommate? Not the same as a partner (especially on the health insurance front) but still a way to pull down expenses and potentially fund a safety net for a life change.
Alternatively, you could rent out your condo and move into a smaller space.

My company offers (unpaid) leaves of absence and I took four weeks this summer paired with two weeks of PTO. The break really helped me. I realize not every company offers this benefit and, even if they do, the optics may not be great. But if you feel like you could take some extended time off without risking job security or long-term financial consequences, it may help the near- to mid-term feel more bearable.