I'd be more inclined to feeling sorry for Clayton rather than Sean.

He whines on about how all of his relationships fail and every partner he has leaves him, but who's the one that causes the problems? Him. He humiliated Marcus at work by storming in and accusing him of having an affair and he was constantly demeaning Billy's job by asking him what the 'gossip' is after someone confided in him. How are you supposed to trust someone like him if your drug taking brother turns up in need of help? Sean is far too immature to have a serious relationship.
I don't blame Eva for telling Billy about Sean's pettiness with the hotel. He only called to re-book it because she forced him to. Then it turns out someone made a complaint about Billy and Todd to the Bishop - of course she's bound to think it's him and she'd already tried talking sense into him after the hotel thing, so the only option was to tell Billy, as his friend. Ok, so it turns out that it supposedly wasn't Sean who complained to the Bishop, but I still wouldn't have put it past him. It's the kind of petty thing he'd do.
Also, since when were Sean and Todd best mates? Sean has always been closer to Jason and Todd even set out to lead Sean on back in his revenge days. Todd may be trying to consider Sean's feelings now, but they were never close friends.
I agree with those that say Sean doesn't deserve sympathy after how he's treated other people's problems. He's completely two faced and bitchy, one minute he'll be acting like someone's best mate and then he'll be gossiping behind their backs as soon as someone happens in their lives. Now the shoe is on the other foot and he can't handle it.
I can't stand his constant moping and self pitying. That episode after he found out about Billy and Todd was torture, I'm glad Phelan told him to grow up. And all this whinging about turning 40 when he's stuck in the same situation he was 10 years ago due to his own choices. He's never taken the initiative to get his own place, he rarely bothers with his son and he hasn't bothered to look for a new job if he's so unhappy at the factory and the pub.
He's literally a teenager in a grown man's body.