Haven't tried it for years TBH. What I can't do back wise is anything where you lean sideways over your pelvis, the triangle for example. Whereas Pilates is mostly linear. I have very little choice of instructors (out in the sticks) but my Pilates one is Body Control trained and that's all she does, she is very good at adapting the group to all our ailments!
I did both for years pre DCs Peace, unfortunately for me it wasn't enough (childbirth related damage). I can't do yoga now because of back problems and you have to be very careful with Pilates if you have even a mild prolapse, which many do without realising it, like me, it can put way too much stress on that area. I still do Pilates (well did till my op and will go back) but can only do it in a fairly limited fashion now, no double leg raises. To be honest the strongest pelvic floor in the world can't prevent prolapse if the damage is there, but it might hold it off for longer.
Erm, I did the Couch to 5k last year and i am now in bed recovering from surgery to repair my prolapse. It didn't all fall out (quite) but I think it's power walking for me from now on . All I can say is if you are going to run, do your pelvic floor exercises seriously too, especially if you have had any difficult childbirth experiences.
I find the best exercise for me is anything where I'm not alone and relying on myself to get out and do something.
Could you and a friend try a new class, pilates is very gentle as a introduction to exercise or perhaps something fun like Zumba?
I joined a local "for fun" netball team 6 years ago and am now great friends with all the girls and we have progressed to playing competitively, the fact I am part of a team means I can't let others down and have to put in an appearance at training.
if you are totally unactive what about starting by going bowling or ice skating at the weekends? thats fun and you'll be burning calories.
If you'd really prefer to exercise alone I'd suggest putting specific times in your diary like you would an appointment - that way you are less likely to find other things to fill the allocated time.