Yeah, illness can def influence supply.
I swear by fenugreek. It was dropped off by a lovely lady from this forum and within 8 hrs of taking it I saw a significant increase. Finally I had to keep taking it till I quit BF when LO was 1yo but it was def worth it.
You can also try marathon pumping sessions to simulate a growth spurt. STick to your usual pumping time, pump till you dont get any more, then take a 5 min break - load the dishwasher or sth - then plonk down and pump again. Repeat this a few times, even if you are pumping dry, the extra stimulation helps.
Otherwise do what you have been doing - put LO to the breast as much as you can. They can def do a better job stimulating milk supply. You can also try pump straight after you have BF LO.
and try not to stress - easier said than done, I know.
Lots of luck:)