Exclusive pumping

My son is barely 5 weeks old. 2 weeks ago he just randomly stopped latching and would nonstop scream as I tried to breastfeed him. I finally gave in and fed him some breast milk by bottle. After a couple days of exclusively pumping, my milk supply completely tanked. I haven't been able to get it back since and have had to start supplementing with formula. Pumping has become extremely difficult and my nipples are horribly cracked. I'd love any advice on how to boost my supply and tips to get through exclusively pumping. Thank you!