Block Milk Ducts

I'm currently 10 weeks postpartum and had been pumping breastmilk for my LO. I keep getting blocked ducts on my right boob and always have to take more lecithin and after a few pumping sessions and massage then it will be cleared. However, this problem just keep coming back every few days even though I'm an undersupply mum. I pump 6 times a day and my daily yield is around 450 to 500ml. Does anyone have the same issues as me? How to resolve it?