Pumpers

Ok pumpers. I’ve been EBF and not started pumping aside from occasional haakaa use. This past week I’ve been pumping when I get a chance(maybe once a day) to get used to the pump for when I return to work. My question is. My left breast always feels fuller and when my LO nurses he seems to like choke on it sometimes. I assumed it was a forceful let down or something similar. Well this week when I use the pump even though that breast feels so full I barely get any milk from it whereas my right breast gives usually triple the amount. So if my left breast gives 0.5iz the right gives 1.5-2oz. Anyone have anything similar or know the cause? Sometimes this left breast feels so full it’s painful. Could it be a plugged duct? Wouldn’t the pump help with that? Thanks in advance