How Can I not be nervous and mess up in softball?

So I think I’m pretty good at softball. If me and my team were practicing, I’d be confident, be having fun, and do well. However, during games, my nerves get to me like crazy. I always feel like I mess up at least twice in a game. It’s like I can’t think straight. I forget where the play should be, sometimes I miss the ball on a grounder for example. That’s a terrible feeling! Right now for high school, we’re doing this “fun” league where we only play on Mondays and we have no practices. Since I’m not ding league this season and have never had time for select, I feel disadvantaged. Almost all the other girls are on select or have some kind of lessons to help them. I have my dad, but that’s not the same and right now he’ll be out for 2 weeks with a broken foot. Any really good advice to help me? This all consumes my thoughts everyday and I’m sick of feeling like this.