Is it wrong to be in a relationship mainly for the well-being of the other person?

I dated this guy for almost two years and at the beginning of my senior year, broke his heart because I needed to find out what I was missing out on in life, if anything. I wanted to go do my own thing and experience my senior year without the commitment to one person. Lots of things happened in the meantime and after seeing him with someone else, seven months later, I realized that I missed him. He had finally gotten over me, and in a weak moment, I put myself back into his life, basically promising that things would be different.

Then, realizing what I had done, I wanted to back out… It’s not the same as it was the first time around. The ‘spark’ that was gone before at the end is still gone, and I don’t know that I’m doing the right thing. I’m leaving for college in two months, and he knows that it has to end when I go, but still says that this is best for him. He is dealing with parent, college, money, work and other issues and I think that what I need to do right now is just stay with him and try to make it the best that I can. I know that he is in love with me, even though I am no longer ‘in love’ with him. I love him and always will, and I just want to help him. Is it wrong to stay in a relationship if there is no spark?

I think that to end it now would just crush him, but if I wait until I have to leave, then it would be easier… because then, it would be because it’s something that I said would happen from the very beginning—not just me changing my mind. I think that ending it now would just cause unnecessary hurt to him and take the only semi-stable thing out of his life. Any thoughts or advice?