Hi darlingdistressed. I understand that the situation is difficult. I think that the best thing would be to talk sincerely with him and tell him why you did it and that you didn't want to hurt him. You could go coulseling together, if it's necessary.
If it doesn't work and you won't go back staying together, you'll have to learn how to be happy without him. It could be long, and maybe you'll need some psychological help. However, you could try to repair the relationship and see what happens.
Good luck