It feels like centuries since I suffered what you are going through (I now have a k pouch) but I still remember the pain and horrors of owning a backside so...
Soak. Soak. Soak. Sitz Baths are your friend, so are bidets, spray bottles of lukewarm water with a drop of some sort of glycerine soap (those bars of transparent soap that you can buy at specialty stores or even dollar stores)...they sooth and ease the pain.
It is the bacteria and acidity that causes the burn, toilet paper only makes it worse. So you need to give your bottom a break...water is your friend...stay close to it...(it is pool season, get yourself a baby pool...And sit in it!)
I have an abdominal stoma and it has been moved 3xs, every time that they move it I get the burn for about 3 months until the skin gets accustomed to the acid and toughens up.
One of my surgeons prescribed an anesthesia cream that put it to sleep for a while (pure relief)...you may want to try that...but not too often.
The Godsend is aloe vera gel with cooling agent and anesthesia...works wonders...really cheap in local drugstores and now that it is summer it is so easy to find...I keep a tube upstairs in the bathroom and you can put one in the fridge too...(yup, it works...hubby can testify to it...for non pouch related reasons )
Hang in there girl...it will get better but you need the tricks of the trade to get you through it all.
Sharon