hey there - I've written on this subject before at length - basically - what you have is known as 'hyper vigilance'. If you pm me Ill talk to you more about it.
It's not your fault and it's based on fears and insecurities that developed in your childhood. You need therapy to sort it out -and well done you for looking into it.
Your mind developed patterns in your childhood, which teach you to constantly search for threats to your security.
You see that it's painful for you and want to tackle it and build new thought patterns - btu I have to warn you, if he isn't supportive then you will find it difficult to remain with him.
There is a very good book by Oliver James, called They Fuck you Up - about how your experiences in childhood affect your emotional responses to relationships later in life.
think of it this way - your mind, at a deep subconscious level, is trying to look after you and protect you from being hurt - it is constantly on alert looking for threats. It is NOT something you can jsust 'snap out of' and it has NO relevance to your actual situation.
you and your husband need to read about insecure patterns of attachment - that is what you have.
I think step one is getting help for yourself, the therapy will also help you communicate all of this to him.
Your problem is common, it really isn't your fault please know that.
Finally - I had the same issue, it was ruining my life, and after a year of thearpy it completely went - believe you can change, you can.