By no way I am I suggesting that this is your issue, however I just wanted to tell you my story.

I am incrediably overprotective of my children, won't go into details but like you have trouble letting other people have them. Even now with my 3 and half year old. Neither of them have ever been away from me overnight. Anyway both are terrible sleepers and I have been chronically overtired for 3 and half years. Some days I feel completley stretched. My doctor had been suggesting anti-depressents to help me deal with the stress and anxiety. A couple of months ago I 'gave in' and starting taking the medicine. It has helped incredibly. I am still shocking with being overprotective but understand a lot of it is my issue. However, the medicine has helped me not to get anxious thinking about all the horrible things that could go wrong.

I also attended a sort of parenting group therapy thing for a couple of months and it really helped me to have a look at what where my issues and how they may be affecting my children. Its all very well for people to say, yes you should let them stay overnight, or let go a bit, but if the thought of it gives you anxiety then you really need to work on it. Doesn't mean you have to let go, just find out where it comes from and then make a decision. I hope I am making some sense , cause its a bit hard to explain.

I hope you find something that helps.