From Women's Aid:-
"It?s possible for abusive people to change their behaviour. However, it?s very difficult to change and so isn?t very common. If your partner has promised to change before and then has resumed his abusive behaviour it?s likely that this pattern will continue to repeat itself.
Unfortunately what usually happens in an abusive relationship is that the abuse increases both in frequency and severity. If your partner is serious about changing his behaviour then he?ll need to seek help either through his GP or through a service specifically for abusive men.
It?s also important to remember that changing this type of behaviour will take time and effort. If he attends a few sessions and then announces that he?s ?cured?, this is unlikely to really be the case. The best perpetrator programmes provide support for the partners and ex-partners of perpetrators, and they?ll be able to give you further information and support.
You might want to take a break from the relationship while he seeks help. During the time that he?s dealing with the reasons why he?s abusive, many issues will be brought to the surface. This could increase the intensity of the abuse for a period of time. For this reason, you may want to consider how to ensure your own safety, and that of any children you may have, during this period.
If your partner is still in any way blaming you for the abuse, then it?s clear that he hasn?t accepted full responsibility for what has happened, and while he?s still saying this, his behaviour is unlikely to change".
He attending an anger management course may not help at all with regards to the domestic violence. It will not address why he is being violent towards you. If he is as you say "unhappy and "lonely" as well these are issues that he needs to address. You are not responsible for him and his actions. He will not change because he will not accept responsibility for his actions.
Would urge you to talk to Womens Aid - its a freephone number and it won't show up on the bill.