Food Allergies Treatment

I am temporarily feeding my infant soy formula for 3 weeks. Partly to check for a milk allergy but mainly so that I may take medication for my Crohn’s Disease. I plan to return to breastfeeding after I finish the meds. How often do I need to pump to maintain my milk. I have been getting about 6 pumping sessions in per day getting 4 ounces each time. My baby is almost 2 months. Is this enough pumping? My breasts seem to be keeping up so far. It’s been 3 days.