So sorry to hear that
Firstly though, its not body fat that oil your joints, its synovial fluid, and over time our bodies make less and less of the stuff. Thats why being overweight won't alleviate joint pain...
My thoughts on the subject are this, and I'm not a complete numb skull, my dad had a cholesterol problem and my niece now has one...
If you are dead sure the meds didn't cause the weight gain and cholesterol, then that's good, it means that continuing them will not prevent you from improving your health.
Knowing its been basically impossible for you to lose weight, isn't it still a viable option to follow a specified diet to lower the cholesterol level itself?
Sorry, this is assuming you don't already have an eating plan in place
If those numbers haven't come down in the past either, maybe using the Statin to assist the specialized eating plan will work better as opposed to using one or the other...
Who knows, maybe if you do it that way the Statin is then temporary?
Well a Dr would know

but yours doesn't seem very doctory at all.
Its after midnight and I've been up since 5am. not tooo sure how articulate this is, and really sorry if its not much help