There's a fact that a lot of peope oversee. Some people just can't do heavy squats. If your one of them, the don't do them. It's as simple as that. People with long legs, en small upperbody tend to have serious problems with squatting. Longer people in general, +2 meters (6,5 feet?), have the same problem.
If you had a hernia, or other serious backinjurie, start slowly.
Or maybe it's a simple problem, and you tend to overtrain your abs and/or back to much or maybe a bad posture at work/general or you're wering a bad belt, too tight?
Start with a heavy legpress, en do the squat second, but just don't push it. You know when to stop, nobody else.