Have you considered an Aussie saddle? Mine feels like my English saddle, but I have more confidence with the poleys & horn than I do without - even tho I don't touch them cantering. Just knowing they are there helps my confidence. The only time I've been really hurt riding, it was using an English saddle. The saddle had NOTHING to do with the fall. I was dismounting when my horse half-reared, spun 180, then bolted. No saddle would help in a situation like that. Still, the change to an Aussie saddle helped my confidence.
Or, canter with a different horse. You mind associates cantering with pain. To change that, you need cantering without pain. And that may take cantering on a different horse until you feel more comfortable.