My baby refuses my nipple !

He is 9 weeks, he breastfed for 7 will but it has been almost two weeks that he is refusing my breasts!

I was using formula too because of his stay in NICU, but recently I don't know what to do !

My supply is decreasing, i started taking Fenugreek pills and i will start exclusive pumping ,

Any tips on how to make him latch again ? It's a huge stress for me