I started conditioning for my sport in school, and I thought I would lose weight but instead I gained 4 pounds? It's probably muscle, but will I keep gaining weight? Or will it even out eventually?

It'll even out eventually. Although I'm sorry to say but I can't tell you when it will even out or what weight you will be when it does because everyone's body is different. You can't make an infinite amount of muscle so don't worry, you will have to level out sometime. So relax and don't stress yourself out about gaining too much weight: That weight is muscle and that's good weight to pack on.