I think you're problem is the opposite and you need more saddle-to-bar drop. Bullhorns can cause a lot of discomfort in several places if they're up too high because you're reaching up and forward when your hands are anywhere but the tops.

Judging by the pic of your bike in your sig link, you may need a shorter stem if you're out on the horns a lot but maybe you could try flipping it to lose some of that rise?