exclusive pumper worried about supply drop

So I've been only pumping since my baby was born, he gets some breastmilk and also formula. Lately he's started to ween himself off breastmilk. I use to be able to get about 4-5oz in 6 hours now if I go 6 hours I get maybe 1.5-3 oz depending. I've tried fenugreek 3 times a day 2 pills each time before and that did nothing. Wondering if anyone else has gone through this that's an exclusive pumper and what you did to help it?