My 8 year old son is the same. He is very emotional and always has been. My daughter is also emotional and so are most of my family. It's just the way they are. It can be trying and worrying, but there are benefits: at least he is showing what he is feeling and not bottling it up. With your help he can learn to deal with his emotions, or at least recognise them. I'm trying to do this for my son and live in hope that this will make him a kind and caring guy.
Oddly, he is popular at school and no-one has teased him for being tearful.