I'm not sure if i understood your question, but i guess you are having trouble keeping a good back position while squating.

Like said here before, maybe you have your feet too close.

Always keep your head pointing up, don't look forward or down, this will help you to keep stability on your back.

If you still having trouble keeping a good position, try using a small plank of wood, and keep it under your heels, this will help too, but don't get accustomed.


If you have a week lower back, i would recommend that you start doing dead lifts, this is very important to give you a solid mass.