What rates and coverage you qualify for depends on your personal details such as conditions, age, previous coverage, and much more. Your best option is to use a multi insurance quote site (they're free) to put your details into and see what quotes you get.
Another thing you may want to consider is, if you're already diganosed and the doctor has prescribed your pain meds is to use prescription assistance. It's designed to help low income people get their meds often for free. It just takes a lot of paperwork. Maybe you've seen the commercials with Montel Williams? the site is www.pparx.prg (for some reason it's down right now, but it's a very active site used by a lot of people, not a scam by any means).