Perhaps you need to figure out where your "center" of weight distribution is in your body. Do you have more length in your legs or in your torso? Depending on that answer, maybe he needs to lift you lower/higher on your hip or rib cage. For instance, if you have a long torso and he's lifting you from a point low on your hip, maybe that's why you're falling forward; so then you'd want to have him try lifting you from a point nearer to your rib cage.