It's not uncommon for patients to have depression after a heart attack -- there is some subtle connection between the brain and the heart that is not completely understood.
It's also common to feel more weak and tired after a heart attack, and you should be enrolled in cardiac rehab (basically a supervised exercise regimen) for a few weeks to months after a heart attack to help get you back on your feet.
Call your primary doctor or cardiologist and see if you can get plugged into this. And if you are experiencing depression, you should certainly talk to a doctor about it, and possibly even start a medication or therapy for that.
I am sorry to learn of your understandable distress. Your physicians and the hospital should provide supportive resources for you. Please contact them directly.