For Fibro and the symptoms I get from having MS. I was 8 years when I was diagnosed with MS and 9 years for Fibro.
I went for a period without taking any meds (6 weeks) and I could have easily been commited to the mental hospital, I was so nutty from lack of sleep, pain and mood swings. When I started taking meds again I could 'feel' my body relaxing too. I assume most peoples bodies are in that relax state most of the time and my illness takes that from me. My sponsor told me no amount of recovery/meetings/readings/4th steps etc...were going to fix my medical conditions.
AA has a phamplet about meds, I think there is a link here somewhere for it.
I also sponsor a lady who takes medication for her illnesses, only after 6 years of trying to 'cure herself' like I did but I only did it for 6 weeks!!! She also mentioned the 'relaxing feeling' and since I don't take the meds she does, I can only assume some of this feeling is actually just 'mental relief' as she's not fighting the pain anymore.
I think a lot of people (in AA) have misconceptions about pain relief (I used to be one) and the good thing about the AA phamplet is it says it is diff for everyone and each person must judge and be responsible for the choices they make themselves.
Dunno if any of that is helpful but whatever you choose will be right for you.