hi WW,
firstly, just sending you some huge hugs.
I don't really know the answer, but couldn't not reply after reading your post.

First things that come into my mind, is has anyone (GP, nurse, etc) talked to you about PND? I really feel you may need to speak to someone, to help you through this.

Other random thoughts I had -
- hormones - you may also be feeling the effects of some hormone fluctuations, given the recent variability in your son's feeding patterns.
other things that jump out at me is that if your son is refluxy and snuffly, these things may be exacerbated by FF, after all, nothing is more gentle than breast milk.
- there is also more work involved in FF - preparing, cleaning bottles etc, something to consider if you are already finding some activities difficult.
- While he is refusing you, and to maintain your supply, try expressing some and even giving him a bottle of EBM to see if he will take that.
- Perhaps too your son is going through a growth spurt or teething, or even a mild illness, and very soon he will again return to feeding, frustrating I know, as you still have to get through the hear and now, but some babies do go through periods of refusal when they are not themselves (one of my twins does, and of course frustratingly it is the one with the weight issues!). He will get hungry again, and as long as he is still peeing and pooing then he will be OK while he is refusing you.

sorry, all very random thoughts, but I just wanted to try and offer you some reassuring thoughts. Good luck. xx