Do you think its more of an emotional/psychological issues since you say you hated your ex and also slept on the couch when married to him?
If its a comfort thing, or feeling that DH is in your space do you need a bigger bed?
My guess is that it may be more psychological since you are able to fall asleep easily on the couch, and your body already has that pattern established from when you were with you ex? I am biased since I am a counselor but I think a counselor could help you figure out how to set a new routine and break the old one.

In my case, I don't sleep well when DH is out of town or not in bed with me. I guess we do get used to sleeping certain ways.

Good luck and don't stress too much about it since stress is likely to make it worse.

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