Why do my breasts burn on let down?

They didn't do this until I stopped breastfeeding and started pumping. It never happens at let downs during the actual pumping, but when my breasts leak at other times. I thought maybe my breast were too full, but they sometimes do it only a half hour after I've emptied my breasts with a pumping. I feel fine, and don't have any redness or itchiness. I had a clogged duct earlier this week, but managed to unclog it that same day. What could be causing this?