21 and frightened

Last December I met my current boyfriend and due to his circumstances at the time I allowed him to move in with me straight away. I genuinely do not believe he had a drug addiction when I first met him although only a couple of months into our relationship I began to notice things were a little odd but never once believed what I was witnessing were infact signs of heroin addiction. In hindsight the evidence was all there.
The black smudges on the wooden floor in the bathroom off his cooking spoon I put down to makeup. Maybe I had dropped my eyeliner and it had marked the floor. I assumed he was cold at night times when he slept in his jumper to cover his track marks. I thought I was just going mad when I was counting my spoons and I felt the same when I was counting my money.
Eventually I found a syringe packet and after finding a cigarette with no filter in days before, I confronted him about it, I didnt shout or get mad, I assured him he could tell me anything yet the explanation he offered was that he had been using steroids and that’s where the packet had come from. I chose to believe him, although because I studied as a nurse I knew the type of needle was for using on veins and that steroids go in to muscle. He became very quiet following this incident and said things like ‘how can you not trust me?’, ‘do you really think i’d lie to you’ . It is as if he needed to make me feel bad inside to rid himself of the guilt he may have suffered for lying to me
Only a few days after this I arranged to meet him outside of a local supermarket after I’d finished work. I waited for an hour. My mum then phoned me to tell me she had discovered him on the bathroom floor unconcious and it had taken her ten minutes to waken him. I ran home, my mum was waiting for me outside, when I went into the bathroom he was sitting on the toilet with his head in his hands. I felt sick to my stomach, he didn’t want to speak to me, he just wanted to get in bed. By the side of the toilet I found a spoon, alongside the cigarette filter and the used needle with the remains of the brown liquid in the syringe. My mum was waiting outside of the bathroom, out of concern I think rather than curiousity, so I hid the evidence and led him to the bedroom, before convincing my mum he had gotten in that state through drink.
It killed me having to lie to my mum, she is the person who raised me single handedly and means the most in the world to me, but at the same time I felt I needed to hear him out before I got other people involved.
He admitted he had been injecting heroin for two months after experimenting with various other highs, legal and illegal, to ease his depression and insomnia. He said ‘the first time I injected myself was supposed to be the last’, and although I believed him, I still felt betrayed that his ‘one off’ decision had led to the sickness, anxiety and shock I was feeling.
Five months later he is now on a methadone programme. It has not been easy and he is still a regular user. Sometimes when we are strapped for cash and he becomes ill from withdrawals, he understandably gets very irritated and restless, but unfortunately this will often result in him becoming angry at me, he says nasty things and although he has never actually touched me, becomes very aggressive. I tell myself over and over again that this is the drugs, it isn’t him, I try to imagine the pain he is suffering, the anxiety he is feeling, and so I never get mad with him. I cry when I am on my own and away from him. I don’t think he considers how his drug use affects me, which perhaps is quite selfish of him, even on his ‘happy’ days I cannot talk about it with him as he becomes very defensive.
I feel as if I have been so understanding and supportive of him, yet he is unable to listen to how I feel. He cannot swallow his pride and talk about his habit. He is very ashamed and I respect that, but I have no one else in the whole world to open up to.
I don’t define him by his drug addiction, and it has never been in my nature to judge anyone suffering any sort of addiction. I love and respect him for the person I know he is. Although we’ve been together only less than a year, our relationship is so intense because of all the things we have been through, I care very much about him and the fear of getting that knock on the door, or worse still, finding his dead body in my bathroom is consuming me. This being said, I enable his drug addiction, it hurts me to admit it, handing him money breaks my heart, but as some of you may know, it is not that easy. I can not see him resort to breaking into houses, robbing or anything like that to fund his addiction, which is what I know will happen if I do not help him pay for his habit.
I am in a very lonely and confused place at the moment. Reading back on my story I feel embarrassed, and almost stupid. We haven’t even been together than long so why am I so bothered? Why do I choose to forgive someone who has stolen from me? Why do I feel so inclined to enable his drug addiction, in an attempt to stop him from getting into trouble with the law? How can i continuously put his feelings before mine, over and over again in a situation he created (whether he intended to or not)?
I really want a happy and normal life, I want to have my own house and children, I want to have enough money to go on little holidays and to treat myself with, I want to go to work and not worry about what I am going to find when I get home, and I want him to be a part of it .. I know I can’t have this for as long as I am with him and he is on heroin.
So do I stick by him and suffer the drug use and everything that comes with it until he manages to become clean, or do I just leave him to fend for himself whilst I get on with my life and start trying to achieve the things I want to?
Am I being naive to think things will ever change?