How's that dodgy nipple going?
It is possible to only feed from one side, but the breast has to get the message that more is needed. If you offer topups then your breast won't make more (does that make sense). I presume though, that the topups are expressed from the other side? So each feed you feed on one, then topup from the other...?
Expressing also gets harder after the initial engorgement subsides - you may be at that point now.