Do bereavement groups work?

My mum died a few weeks ago, and the pain of losing her is just getting harder. Yet the patience of others' is wearing thinner, and I don't like to talk about it with anyone really. I just cry a lot when I'm on my own. I'm not religious personally, so have looked up bereavement groups that aren't connected with church and there is one in my local area. Has anyone else been to a group? Do they actually work? I'm nervous and shy to attend one - I'm not a nervous or shy person, but this is an emotion that is so very different to anything else I've ever experienced. What usually happens at these things? Are they just a big cry-fest? I don't know what to expect, so if anyone can give me an pointers I'd appreciate it. Thanks.