Nauseous

I had my baby September 17th. Since having him I can hardly eat. Every time I try to eat or just thinking about eating makes me want to throw up. I’m able to eat a few bites or maybe a VERY small bowl of something but I still feel sick to my stomach and can hardly finish whatever I’m eating. I’ve been drinking a lot of water to make up for the lack of food but I’m not sure what to do about eating or if there’s an underlying issue that’s causing this?