How to handle being ostracized at work?

I'm so miserable and tired of getting shut out by my coworkers, who used to be friends of mine. I try to be strong and not let it get to me. I would understand if I was difficult to work with and a bitch. But I'm not, I'm always nice, kind, respectful. I never make any conflict. I had to miss work for five months because of my spouses accident. When I got back I was completely ostracized. No one will tell me why, I just get silent treatment. It's just tense and awkward all day long. I've already been thru hell because of this accident, and these awful people know that. So they just pile on the stress and sadness and anger for me. I have no friends now and I have no idea how to make new ones.