Ive been squatting for a while now 4-5months and i notice now that as i go higher in weight I tend to or sometimes I notice that i some go down to fast. Im pretty sure this is part of or due to having a weak core. I was wondering what exercises help strengthen it?

I wouldn't think it's totally becuase of a weak core. The simple fact is, you just have to slow down and concentrate on the movement. If indeed it is your core, if you slow down, you core will catch up eventually.

Try some planks, side planks, barbell rollouts, jackknifes and bird dogs.