Getting out of control

Im at a point in my life where I thought I could handle things with my father. You know him being a drug addict my whole life i thought the older i got the better it will get since im older and i can just leave the house whenever. It has turned out to be the complete opposite! As i grow older i start to wonder if my dad going to be a drug addict forever? Will he even get a chance to meet my kids when i want children. So many things run through my mind. Im afraid of moving out and then getting a call that my father died or something. Im not in high school or elementary school anymore. Im in college where my grades really do depend on my career. Im doing horrible in college and thats not what I want for my future. I just feel like im going downhill. Im about to be 20 and this is not where i want to be in my life. Im not doing good in college because i have been so depressed. I hate even saying that word because it does scare me. I feel like im bi polar now and everything annoys me and i just cant ever be happy now. I have never been this sad before. I seriously thought my dad would get it together and in one month ill be 20 and what things are still the same? I cant live like this anymore! Im always crying, always hurt, i cant sleep, i can barley eat, im always calling him to make sure he isnt dead and im always making sure hes safe when hes sleeping. I feel like im taking care of a baby. I dont feel like myself, im usually so happy and goofy and im always cracking jokes with my friends and partying and just having a fun time and thats not me at all anymore. I sit in my house doing nothing but sleeping or watching over my dad. I feel ache and i  sometimes feel nausea. I just cant take it anymore. Im so torn to what my next step is. Do I kick my dad out? (Hes staying with me and mom) Do i tell him to leave? I dont know why but i dont have it in me to kick him out.. why? Because i cant dare be in a warm house while he is outside in the cold, i cant dare leave him out there when im not watching over him and i dont know if he will over dose and die. i just cant stand that! But him being home with me is making me and mom so depressed.. My mom has lost 8 pounds in a week because she barley eats to. He is tearing me down little by little. I dont know what to do. My grades are bad, im failing at everything in life right now because of his addiction. He was sober for 8 months up until 3 weeks ago. Thats why it hit me so hard because my life was finally starting to be wonderful and now we are back at it. Its not fair to me or my mother! I need advice.