How to deal with a recent breakup?

Hi doctor,

I am a 20 year old engineering student. Life has been good to me for all these years. Eight months ago I met a girl, and since I met her, I have not spent a day without talking to her, and it was a long distance relationship. Now, I was very inexperienced when it comes to love as it requires to trust another human being. I have fallen for her so deep that I have forgotten myself, my life, my habits, hobbies and cause in life. It is like a mind enslavement, other than physical slavery. This person has requested more and more from me, and I was unable to set boundaries. I have become a shadow of her, pick up her habits, her beliefs and fearing that she would love me less for who I was. I would try to comfort her, even if it was something that defies my logic. For eight months, I have been living encapsulated into another person. I have failed my exams and was unhappy that I could not stay with her all the time. Every night I would struggle to fall asleep. I have been wasting my energy on planning future with her. I jumped 10 years ahead and started worrying about things. I would hear someone talk and fail to follow after a couple of words, because of daydreaming. I have been on the verge of snapping several times and felt like death was the only solution. Until a few days ago, I chose to live and be myself again. I physically felt relief. I have stopped worrying so much about others and cared about me. Life felt different all of a sudden. I am on my way to recovery now, and my past haunts me. Whenever I remember how it was, I feel terrified. I also feel that I have done significant damage to myself. My brain has become more sloppy. I have taken depression drugs in the past and sleeping pills when I could not handle the pain. I am starting to learn about myself again, I have forgotten how I used to be. And it feels so weird to be in that place, but very healthy. I am caught up in all this mess, and I would like to hear from others.