Spit up

When to be concerned about spit up?

we've been trying different formulas to help with constipation. well our daughter has had the normal spit up and also projectile spit up several times over the last few days. she spit up a lot during our hospital stay and thats why we went with a sensitive formula, then she became very constipated, so we switched to a soy and it was worse and last night was the first night on enfamil gentle ease. she for the first time spit up through her nose and mouth and stopped breathing for a few seconds, I went into choking/cpr mode and luckily it helped and was over within a few seconds that felt like forever.

did we change too much too quickly? could it be a reflux issue? we had a huge scare last night and I can't sleep over it. I'm calling the dr today and know we will get scowled for changing formula but we're trying our best...