Is this my appendix I found or stage 1 colon cancer?

This could be you are compressing one of your great vessels that go down to your legs which would give you the "vibration" as the blood tries to p through the narrowed vessel because you are pushing on it. This can only occur in skinny people because most people cannot reach this vessel and compress it because there is too many layers of fat. Stop compressing this because you don't want to impede the normal functioning of your body.