Hope I’ve read this right, OP. It seems to me that you might want to swap your bedroom for another one. Decide on that first, maybe. Then decide whether you want a dedicated bedroom or perhaps more of a second sitting room with space for other furniture? A good quality sofa bed would allow you to make the room into something other than a bedroom. If you feel the decoration is too bland, you can always change accessories, cushions, curtains etc., to include some new colour.
If you’re sticking to a normal bed - unless desperate for space - I’d never want a single bed. For sheer comfort, I’d opt for more space for myself. After many years in a narrow single (her choice) we encouraged my Mum to buy a small double - she loved it. Like Witzend, I believe duvets should not just sit on top of the bed, but hang well down all around. Nobody wants their duvet to move each time they do, so to be able to turn underneath it and stay covered, it’s better to use a bigger duvet than the mattress size. For a small double, using a normal double sheet would give you sufficient tuck-in to avoid having to strip and remake the bed almost every morning, which is what happens when sheets are too small ! No point in looking for work!! ?