so, I failed at my last attempt to get into cycling and loose weight. Basically it was so uncomfortable seat wise and suspension wise(ie it had none) I just can't use it at my current weight of 22stone.
I'm deliberately playing devil's advocate here, so bear with me...
Cycling IS uncomfortable when you start. You will have a sore arse, your legs will ache, as will your back, shoulders and many other parts of your body. I've been cycling for decades and after a normal (for me) ride I have virtually no pain, but if I go on a significantly longer ride than normal, or really push myself hard I still feel as if I've gone 12 rounds with Frank Bruno

when I get home. (Showing my age there - substitute a current boxer if you're significantly younger than 51!)
Do you need to accept that initial pain and push through it?
Get a bike that fits and a decent saddle and go for it! Good luck.