Actually, the unfortunate truth is that, or some pp, as long as u don't pump on the dot, u might be prone to blocked ducts or lumps. I am one of them, too. I pump three hourly too, but once, I was out buying something and dragged the pumping time till 4 hours. Before I knew it , there was a lump in my breast and it hurts. The milk supply also dropped.
When this happens, you really have to endure the pain and massage your breast REALLY hard. Cup your breast with your hand (with your nipple sandwiched between your index finger and middle finger) and massage strongly. It will hurt real bad. Endure so that the lump will loosen. If u cannot bring yourself to do it, u might have to approach a lactation consultant to help u. One tip is go for a hot shower first before massaging. Cold compress or cold cabbage will reduce pain but will also reduce supply if over-used.
I'm sorry that this had to happen to u, but it does happen sometimes. Endure and after u go through it, supply should resume. Be diligent with pumping, otherwise lumps will return. If u r planning to wean in future, do it gently by extending your pumping time by 15 min each time.
All the best.