You lifted all those weights as a way to get better for lacrosse. During the off-season, you spent lots of time in the gym, and less time on the field. Now, as the season approached, it's time to shift your focus to the field and "peak" for lacrosse.
Your job in the gym was to lift weights. Nobody cared how many ground balls you picked up, or how many assists you had. It was time to build a big squat!
Now its lacrosse time. Your teammates want you to produce on the field. They don't care how much you can bench press or how big your arms are.
All of that said, you're probably doing a lot of running and long sprints. That kind of stuff burns LOTS of calories. Be sure to eat enough, especially enough carbs/fat to fuel all that exercise.
Also, I think L-glutimine is a great supplement for building/maintaining muscle.