Good, I am glad to hear you have the dr appt. Was it today? How did it go? It might be that you need a different med because of the chemical changes after giving birth. And that is ok. Your support group will be helpful. Being around adults actually helps during this time, even if it is to get help for your mood.
Don't let this stop you from deciding to have more kids. It will go away. It is temporary. I spoke to my ob/gyn who did say he recognized my depresssion with my second (but never suggested help at the time) and he told me there is only a finite period of time to expand your family. That I can't let this stop me when it is not a permanent thing. There is help. There are things you can do. And you may be totally different with your second. Plus, your dr can take this into consideration and may end up changing your meds to be proactive with your second. Don't let this let you feel defeated in any way.
In terms of the feeding, he is 3 months. Feed him then take him for a walk. He shouldn't need to eat again for at least 2.5 hrs or so, and at 3 months maybe a little longer. He will be able to start solids soon (and do that cause he is growing). He may fuss. Bundle hiim up well so he is warm. They do say that fresh air helps with fussy babies, and walk fast - keep him moving. And sometimes he may fuss but you may need to try this a few times. My oldest used to fuss but if I pushed him fast on bumpy roads - he was seriously fine (I was careful!) but that might be what it takes.
My post partum does not sound as intense as yours, which is probably why I never had meds. But allow the med switch. Don't be afraid to be honest with your dr. Know that this is normal, and it will pass. Feeling solely responsible for another human being is alot of stress, but know that babies (kids in general) are pretty resiliant. Feed him. Hold him alot (that is a good thing). Keep him clean and warm. And you are doing JUST FINE!!! As I said, pm me if you need to talk. I feel for you. And let me know how the dr appt goes