When my baby was smaller I would actually sit on the floor in front of the potty and set her on the potty in the sitting position with her bum hanging down in the potty just a little. When she got bigger my arms would tire and so I got a potty seat to put on the potty so I didn't have to support her weight, just had to keep her from falling over.<br><br>
Also, (I have never actually done this so not sure) have you tried maybe sitting on the potty behind him? Maybe let him straddle your legs even?<br><br>
My baby has always been very chunky so I know how you feel, there is no way I ever would of been able to hold her as you described. I have a bad back to begin with.