HELP, After Benadryl, my breastmilk supply is drying. Can I get it back?

It’s 6am and I’m sad and crying. My baby is one month and my milk supply is going down. I wasn’t aware that Benadryl wasn’t a good option when nursing so I was taking half a pill before bed. I’ve been drinking water, oats, pumping, milk tea, lactation drinks and it just keeps decreasing. Does anyone have any tips for a desperate mom? I feel like a failure and angry at myself. No one at the hospital told me Benadryl was a bad option and since it was administered to my after my c section I thought it was okay to take