We can't leave each other alone (Female Water Dog & Male Fire Tiger)

I am a Water Dog and I've been interested in a Fire Tiger for the last 14 years. He lives in a different country, so that's why we haven't taken it further. We have many misunderstandings nowadays and can't seem to talk for longer than 2 weeks before we drive each other mad. This has been like this for a few years now. I've recently discovered that he has been seeing someone else for quite a few years, which he never mentioned. I am very angry about it but we can't seem to leave each other alone. I know that water and fire are not compatible. Is that why we irritate each other? Also, could the fact that Tigers and Dogs are so compatible be the reason he still pursues me even though he's in a relationship. He doesn't understand why he does it and tries to stay away but can't.