DH eats, sleeps and breathes a sport. He cannot seem to talk or think about anything else. If he's ever texting, it's about the sport, ruminating over a game he has played or watched, or even scenarios his fellow sport fans send to him about their own games or games they watched. If he can't play it himself, he watches it on television. If he has to sleep, he watches it on his phone in bed with earphones in, in the early hours of the morning, the phone lighting up the room while I'm trying to sleep.
It's all he texts me about when he is out of the house. That he played the game, he won or he lost. How he feels about it. What everyone else who is there thinks. That he watched a game, somebody won and somebody lost. He's happy or he's sad depending on who he likes and whether he thinks it was fair.
When he's in the house, he talks AT me about the sport. Philosophical conversations we have as a couple get shunted on to an example involving the sport, then once we are safely back on sport territory, he continues on it.
When we're out with friends, he drags conversations - kicking and screaming - on to his sport. People indulge him for a while, but when it seems he wants to carry on, they make excuses to leave or start a new conversation (actually talk over him.)
I have tried to take a small bit of interest, hoping that will encourage him to feel his interests are appreciated and will solicit return questions about things I'm interested in. No. It makes him speak for longer and longer about the sport, in a "let's start from the beginning" kind of way. Then he gets overwhelmed with how much he wants to say and ends up giving me the complete history/backstory, right up to the answer to my question and beyond.
When he's finished (answering my polite question,) he will sit back and say that he really feels we've bonded tonight. That it reminds him what a great partnership we are. 
Is this selfish behaviour or obsessive behaviour or both?