Does height matter if you play midfield your about 5'7
Technically everything matters, but realistically no.
If you love the game, Play it.
And in Lacrosse that is true more than any other sport. I have seen extremely good tiny players 4' 10" making huge impacts on teams. To be honest the size of your heart is WAY more important than the size of your body.
Obviously if you are big and fast and agile and smart, with good hands, quick feet, is better than if you are tiny, slow, dumb, cant catch a cold, and you trip over own feet.
And of course it depends on what level of Lacrosse we are talking about. If you are pre-high school don't even consider it. Play where you want. If you are upper levels of high School on a very competitive team, then size matters a little, but really not much. High competitive College lacrosse or beyond of course the elite players are going to be those kids who are the best biggest athletes.
How well you move? Can you take a hit? Are you tough? Do you have good stick skills? Do you understand the game. Are you coachable? Do you listen to your coaches and do what they say? Is your technique good? Focus on those things. Those are things you can control. Forget about how tall you are. That you cannot control. No one who loves this sport should be afraid to try because of your size. This is not football, or basketball, or even hockey.