RE: GEL I don't know how he feels physically. I know his back bothers him...that's pretty much a given right now....but I don't know how he feels due to this freaking kidney stone.
I had 1 back surgery and was supposed to have a second but chose physical therapy instead.
About back pain and sex: (Your H's back condition and problems may be different so my information might not apply)
I do one exercise while laying on my back on the bed where I suck my stomach in, tilt my pelvis toward my head, flatten my back against the mattress and hols that for 10 seconds and do it 10 to 15 times. It is easy to do and feels good.
Translate this into ML.
Just put BB on top and let me do some or most of the moving and this is how we have sex. It just worked out this way because BB does not want much weight on her during sex and she wants her back and hair rubbed during coupling. I can do this except on all of the really bad days, which might be 10 days a year, which leaves 355 days a year to ML.