How do I deal with feelings of guilt and shame related to how long my PhD has taken?
Talk to a counselor about your feelings. They can help.
But you aren't alone in taking a long time. Your disabilities are part of it, but success in research can't really be scheduled. Depending on the research questions you've been asking your extra three years (say) can be perfectly normal. Insight comes when it comes. And, I suspect you've had necessary timeouts for medical reasons.
But you are probably feeling a bit of both burn out and possibly imposter syndrome. Both are common at the end of a doctoral program, even if it doesn't take longer than (whatever it means to be) normal.
Congratulations on finishing. Thank everyone who has supported you.