You would have to stop whatever birth control you are on
hmm, I've heard that can happen with hormonal birth control... maybe try pumping more often or adding in some oatmeal? it worked for me! here's what the 'Heal App' says.... "It's understandable to be concerned about your milk supply, especially after starting the birth control patch. To help improve your milk supply, try to breastfeed or pump more frequently, as increased stimulation can signal your body to produce more milk. Staying well-hydrated and ensuring you're consuming enough calories can also support your supply. Additionally, consider incorporating lactation-friendly foods like oats, fenugreek, or brewer's yeast into your diet. Have you noticed any specific changes in your breastfeeding routine since starting the patch?"
Progesterone only birth control should not impact milk supply