First, I'm sorry for your loss. I can't imagine the pain.
Our dreams are not "real" as they are made from memories and the mindset we are in. I read a lot of scientific reviews about dreams as I'm very curious about it. For the same reason you wonder what your dream was about : sometimes it's so vivid you can't tell if it's real or not. When a dream is very strong and gives you the feeling that it was real, is because it's about an important subject for you. We don't know why we dream exactly but we know that those intense dreams are about something bothering us. Never analyze it like if it's real, like if it has a clear meaning and answers. It does not. It does never say what to do, how, or why. But it tells you it's a sensitive subject for you and you should work on it. Maybe with the help of a therapist, if you feel like it.
You are maybe afraid of having done something wrong with your husband, and of course, to make him feel bad now he's gone. If it's what you think deep down, please remember you are a human being, and as every single one of us, you made mistakes in your life. Don't blame yourself too hard for that. I guess, reading your post, that you two really loved each other. This is what in my opinion you have to keep in mind. That love won't go away, it's the most beautiful thing in the world in my opinion even if it's hard to think about it without being very hurt.
I truly wish you the best, because I feel like you are a very kind person who deserves the best.