You need to go see your doctor. Postpartum depression is not something you want to delay treatment in. There isn't enough vitamin D, exercise, alone time, etc. that is going to treat postpartum depression. Please go see a doctor. As an RN, I can assure you that many women feel this way and we're here to help you feel better so you can take care of yourself and your baby. Medication is what will help you, I promise.
Make sure your getting outside, going for walks, getting regular exercise and making it a point to have time just for you.
Most likely postpartum depresion. Its when after kabor you get sad angry depress and just sad you start feeling very bad and depress maybe even cry at times. For this you need to tell your doctor because well depending on how you take it it could be dangerous. When you tell your dr she or he can give you some medication for it that will help you so much. This happens to many women after labor so dont be afraid just tell a dr so you can control this!