Welcome. You're fighting far too much heads up trim to fix by moving your legs/head/butt. You need to shift some lead.
"Some weights in hand" trim exercise:
An exercise to do is take some of the weight from your belt and hold them in your hands.
You can still manipulate your inflator valve/mask/regs by putting all the 'hand' weights in one hand temporarily.
Descend in the pool
Extend the weights out in front of you and play with how far in front you hold them, (chest, shoulder, head, full arm length in front).
You should find a point where your body can be very level and in trim with little corrective effort from your legs.
Then hold it there while you play with your frog kick to move you about a bit.
This should give you a better idea of how little effort can be required to stay in trim, and how much weight you need to shift how much higher.
Typically, in trim feels a bit head down to the diver.
I have no connection to UTD, but their Scuba makeover videos demonstrate this trim exercise, though before putting the BC on. You could always do it sans BC by floating the BC above you.
Now you know what an in-trim weight distribution feels like. Doing a normal dive with weights in your hands is not very practical so some location needs to be found on your gear. Achieving that with what ever BC and weights you have on hand is a separate step that gets into details of what you have to work with. On the tank band moves it up from the waist, as does on the tank valve, but both also move it further behind your back when you are level and increase your tendency to roll belly up. On the top curve of the shoulder straps is fairly ideal for affecting weight distribution (it's almost as high as it can go and is inline with your body front-to-back) but can clutter up that area and is often hard to attach there with a jacket BC.
