PP - its up to you. But one word of advice. When i had Mia on the reflux formula she found it so hard to bring up her wind coz it was heavier than normal formula. so fix one and get aanother iykwim. Not that it fixed her problem, her spews were just really thick so she would gag on them every now and then. Expressing does mess with your supply... have you thought about getting him a thickner to take before a BF??? that way hes having thicker breastmilk and may be able to keep it down better?