I don't yawn or get watery eyes I giggle. And I've noticed it's only when I'm working with a specific feeling if I just play it with no specific emotions or memory in mind I don't do it, I think when I giggle I am definitely getting results.
That's very common but not everyone does. People vary quite a lot. And individuals can react very differently depending upon what's being worked on. Ive seen very varied reactions whilst working with people in a therapy setting. The question is not so much whether that's normal but whether the tracks are working for you. As long as they are then you're doing it right. Well done!