I'm going to go with Chug on this one, your PADI peak performance class didn't do you any favors, that is WAY too much weight, entirely unacceptable for a class like that to weight you that heavy.
In similar configuration in warm salt water without an exposure suit I wear about 6lbs of lead, that's for me, a transpac/wing so no inherent weight there, and an al80. With a 5mm full wetsuit I might add maybe 10lbs to that for salt water, about 6lbs for fresh water. I'm 6'4" 280, built pretty solid, but certainly not the skinniest guy out there. In a 3mm wetsuit for your size, you shouldn't have needed more than about 16lbs of lead total, certainly a far cry from 24. You need to do a proper weight check, and there are two ways to do it.
Weight your gear, should be about 6lbs for a stab jacket and an al80 in salt water
Weight yourself, should be less than 4lbs
Weight your wetsuit, should be somewhere between 6-10lbs for a 3mm depending on brand and what not, should be about 6-7lbs in fresh water.
You'll add a few lbs for salt water, so you should come up between 16-20 real world worst case
Alternatively with a full tank you can weight yourself in your wetsuit and add 4lbs for the tank. Either way have to come out below 20lbs, and should be somewhere around 16.
If you were putting your weights that high on your body, your trim was wrong and it pushed your CoG too far down, this is not surprising in a PADI class when you are flutter kicking, but with that relatively small amount of weight on your belt which is about where your CoG should be, your trim shouldn't be a problem. A BP/W will solve a lot of your problems, and if that isn't enough weight harnesses exist but frankly you should be embarrassed if you have to use one in anything but a 7mm farmer john or a drysuit. Not to shame people, but if you are needing one in anything outside of those two types of exposure protection you either need to go on a diet because you are not in good enough shape to dive safely, or your are so far overweighted you are a danger to yourself and the environment that you are liable to come crashing down onto.
Edit: just saw that you were using a AL100, using that amount of lead is entirely unacceptable and your instructor needs to go back to the books on how to weight students, especially for a peak performance buoyancy class, obviously this is outside looking in, but I can honestly say I have never seen someone need that much weight for a 3mm with that tank, I've seen 2 people need that much weight with AL80's, but they needed over 10lbs to sink themselves....
many years ago from the last time I dove with a single tank on my back, but 5mm steamer, HP120, so 1.3lbs negative instead of 0.5lbs negative on your AL100, but didn't wear a weight belt, DiveRite Nomad was the BC so there was no negative buoyancy there. This was in fresh water, so would have required 4 to 6lbs if I was in the ocean, but I was properly weighted. Granted I do sink by a few lbs so that helps, but most people are less than 4lbs positive inherently so you don't need that much.