Fix a screw into a wall-plug
It sounds like a longer screw of the same diameter would solve your problem.

If that doesn't work try a slightly larger diameter screw.

You can help stop this problem from happening again by adding a spacer between the hook and the wall. The spacer can be of any material. It should look like a thick washer. The thickness should be whatever is now the distance between the hook and the wall. The diameter should be about four times the thickness. The hole should be only large enough for the screw. This will allow the screw to hold the hook tightly and prevent it from wiggling and working the screw loose again.

Once you know the dimensions of the spacer, a hardware or DIY store can help you find it.