resent my relationship and want to end it.

Really looking for some advice from anyone who has been in a longterm relationship... im about to end my 5 year relationship with what was the love of my life. Im scared i may regret this decision until the day i die and i just dont want to look back 20 years from now and be childless and alone. im only 21 and ive been living with him since i was 17 so he feels like home to me. im afraid im walking away from my only chance at happiness, im afraid hes going to marry someone else and be happy and i wont. Im not looking for something better, im not searching for something more exciting, im just so so miserable every day and i feel like i might be happier alone. We fight every single day, sleep in seperate bedrooms for days at a time, we name-call and threaten to leave eachother every week but we say we love eachother. Hes sweet and caring, he tells me im beautiful, he cooks for me, compromises with me and overall treats me well - but we fight, everyday. He uses drugs and i dont, hes unemployed and i work everyday, he watches t.v all day long while i run around trying to organize our finances, our home- our lifes. He does not contribute to our relationship at all, but he loves me. I feel like a selfish person to walk away from someone who i feel adores me but im sick of feeling like im doing it all on my own. Truly- i resent him, i love him but i do resent him. I resent him for not trying to lift the financial burden off of me, for not caring about himself enough to quit smoking weed, for not having ambitions in life and for being a weight on my shoulders. I love and care about him and dont want to see him unhappy- but i just simply cannot do this anymore. Am i just being selfish for expecting more from him when he tells me everyday he cherishes my love for him.