For squats, if you can't manage a barbell on your shoulders, you can always hold dumbbells in your hands. Don't know if you've tried that.

And I think most people can deadlift higher weights than they can squat. If your gym has lighter barbells, you might want to start with a ten-pound barbell and see how that feels. You'll just need to elevate it a little so you're not having to bend down too far to pick it up--it should be at the height it would be at if it had 45-pound plates.