What can I do to bulk up?

I'm 23 and and I've been trying for years to build muscles. I lift weights daily, I jog, and swim. I also bike and rock climb. But I'm still a wimpy buck thirty and my ab muscles are pretty much invisible. I'm afraid to take supplements because of all the stories I've heard about having to keep taking the supplement or else I'll gain all the weight back. Are there any other, safe alternatives to help me gain muscle mass without the dependence of supplements?