I have had exactly the same thing as you! A really sore, weepy wound right next to my stoma! It carried on for 3 months and nothing I did helped, until I started using steroid cream applied onto a small piece of silver-based cotton dressing (Aquacel). I would place this directly onto the sore area, cream side down, then use some Comfeel cut out into a half-moon shape to go over the dressing that was on my skin. This kept the cream on the wound but allowed the bag to stick properly as bags stick to Comfeel. I changed my bag every day and sometimes every 2nd, and it slowly but surely started to heal. It's been 4 months now and my skin is healed up, but if it gets too moist it breaks down again, so I just start with the cream/dressing (Aquacel)/Comfeel combo. I hope this helps.
PS.. My skin problem was also pyoderma gangrenosum, not very nice at all and very hard to heal, and the sooner you get onto it, the better. For this, the powder doesn't work, you need something more like an AB cream. It took 3 months just to diagnose as doctors try to eliminate first, took a very good wound specialist to recognize it.