I have a playstation 2 slimline model.

Your laser lense is more than likely dirty. It's not too hard of a fix. I recently had to clean mine. MAKE SURE THE POWER IS OFF! Unplug the unit, take out the screws on the bottom, then, when opened, take the screws out of the top of the disc player. Your laser lense should now be exposed. Gently clean it with a Q-tip and rubbing alcohol. Reassemble. Good luck!