I am not an expert on either Colgate or CMU so maybe others can comment on those.
Regarding how you can improve, I would try and rock your finals and get all A’s this semester and also get A’s in the autumn as well. While the laws of Math will prevent your GPA from increasing too much at this late stage, an increasing trend in GPA is a great thing.
Lastly, you mentioned that you are retaking the ACT again which is a good thing. Try and get your Reading component up on the ACT as some schools subscore the ACT. Also, study hard and try and rock your SAT Subject Tests, if you can get those 750+ that will be great as you will need 3 good subject scores to apply to Georgetown.