Disclaimer: I am a birth father. Depression years after adoption?

Hello everyone, Three and a half years ago when I was 18/19 and a sophomore in college my girlfriend got pregnant. We are both religious and come from religious families and chose not to get an abortion. Although never explicitly stated, we all knew that my plans of going to medical school were a huge part of why we chose not to keep our beautiful boy. While she went back home to be pregnant and have the baby, I stayed at school and continued my pre-med studies. I drank and smoked heavily which can be almost normal in college but for me it was a way to deal with the pending adoption. Now 3.5 years later, I am a second year medical student wracked with guilt and emotion about my decision. Basically I am wondering if anyone else took years to have an extremely sad depressive/anxious reaction to their adoption? To all the birth parents reading this, I love you all. No one can know the pain we have experienced without going through it first-hand themselves