Im comfortable in my stance.
My front-leg is slightly behind my back leg because I can step into the pitch better that way.Heres where the problem comes

Right as the pitch is about to come in I tend to raise my upperbody thus changing the level I see the ball at and I hit a grounder.

I didnt do this the other day and I went 2-4,hitting solid contact all the way.Today I do that and I go 1-3 with a walk,a ground ball that shouldve been an out(error on the SS)and a base hit.Whats the best way to go about breaking this

Since I am playing varsity now I need to fix this fast so my hitting isnt effected.Thanks in advance

First of all, don't panic!

Baseball is a game of ups and downs, so don't think due to one day at the plate, that you have totally changed. It could be that your legs didn't feel as fresh resulting in you coming out of them early. It could be that you weren't seeing the ball for some reason and your body was trying to make adjustments in flight to see it better (although that wouldn't help). Don't go making any big changes right now. See if it works itself out.

Something you could do is to video yourself and again when you have another great day as you did the other day; compare the two videos and see if you can see any changes. Sometimes what you feel isn't always what it is. Keep swinging it, stay confident, and you will be fine.

Good luck!