My boyfriend has no prospects...?

I have been with my boyfriend for nearly 3 years. We have been through quite a lot, he is 22 and I am 24. He cheated on me after us being together for 6 months, and I suppose I never trusted him fully since that happened despite me not mentioning it again. We have 17 month old twins and live together in his hometown. He has a part time job at a supermarket and no qualifications, spends his time watching tv or playing the playstation. He is great with the twins and spends time with them, often does the dishes and looks after then so I am by no means saying that he is a waste of space because he is far from that. However, I feel like his mother a lot of the time. I have to keep pestering him to help around the house and to look for a full time job or do something to better himself. I have to go to college full time and work part time so rarely get a day off. I do this because otherwise we would be on the poverty line and I want better for my children. I just want him to have the drive to get a full time job and become an adult. He finds it difficult to read, so I spent ages looking for somewhere that would help him and all he has to do is call them up but he hasn't bothered. It's been nearly a month and I mention it every day but the only person that can do something about it is himself. It's like he doesn't mind being stuck the way we are, but we are slowly getting into my overdraft because we don't have enough money and I am getting worried. We argue all the time because I genuinely am so frustrated at his lack of ambition. I don't want him to change his personality, but I want him to grow up and take charge of his life. I feel like I have three children! Please give me some advice....

may i just add that my frustration got so bad tonight, that I had a massive go at him and I called him a "loser". I feel really bad for this, but I am so angry at his lack of motivation. I feel really guilty and this can't go on anymore