My DP and I slept in separate beds for years. We adored each other but he was the hottest person I have ever known and I am the one who sleeps with no duvet and the window open all year. It simply didn't work for us. Our relationship actually improved for it as neither of us woke up grumpy after a night of being uncomfortable.
Try to reconcile yourself to it; if you stop thinking that you are 'lonely' then it will be easier. Look at your relationship apart from this issue, is it good? are you generally loving towards each other? do you have a cuddle before bedtime? To me the cuddle before bed was the best... my partner died very suddenly at work early one morning and the last time I saw him we were standing in the kitchen having a goodnight hug and I have that memory forever.
What happens if you go and climb into 'his' bed with him? This was also something we regularly did and with no hard feelings when one of us moved to sleep.
When you think about it, once the first throes of passion are exhausted, sleeping with someone is rarely as easy as society would have us believe. Restless legs, getting up for a pee, getting up for children, a night when you can't sleep, too hot/cold, one of you unwell, a random (heavy) arm dropping over you just as you drop off... the list is endless.
It would help you greatly if your OH could explain why. There has to be a reason and then you could work from that point. Just be careful not to destroy an otherwise good relationship by causing WW3 over it... looked at in a different light, the point of bed is actually to sleep so whilst you are asleep you aren't really missing him.