Model for Keeping Weight Back?

I’m a college freshman pitcher and one of my biggest problems is the my lower half moves faster than my upper half. A lot of the time my hips will open up early, or my arm will be behind, or probably a combination and over the course of time this also influenced my arm circle in ways. I’ve been spending as much time as possible getting my arm circle complete again, trying to use more hips and keeping them closed longer. Also I’ve been trying to keep my head over the center of my body when I throw although I have been limited by the amount of video that I can use.
I was wondering who a good pro to watch and model these things would be. I will try to post a video asap with some of the work I’m doing but I need to get lower half involved, and most importantly I dont think I’m using my hips well. I mean I have problems with my upper half including arm circle but I’m hoping that this will change once I get my lower half straightened out. If you could just post a link to a video or even just a player to watch that’d be helpful. I’ve been watching a bunch of gerrit cole because I like how quickly he gets his hips though.
Also a few drills to help me work on these things would be helpful too. Thanks!