By leaving the bed you once shared you've begun to relearn how to sleep and associated good sleep with your current bed. Once you've worked on your habits, know your needs, and find a sleeping pattern that suits you, you can gradually try to return to your shared bed. It's possible that this bed reminds you of poor sleep, even insomnia. It may generate worry and anxiety.
If that's the case, start by making it a pleasant space!
Maybe you can declutter the bedroom if there are things that aren't related to sleep, change the sheets, change the curtains - make it a new room. Then gradually return to this bed. Start with one or two nights a week, perhaps during the weekend when you don't have to get up for work. This will stop you from worrying about having a bad night and not being able to perform well the next day.
Once those first few nights are going well, you can gradually increase them.
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