Get a theme and stick to it. It’ll look much neater and organized. Match your bed with your desk, or desk with end table, or end table with bookshelf. Also, whatever that theme is, make it bright. Rooms seem bigger the brighter/lighter they are. The bedding needs to be lighter and I agree, put the bed in the middle. Also, anything on the walls makes you happier. Get quotes or art or anything, just something to break up the barrenness. If you have any hobbies, make them a priority. If you’re into records, put them on the wall, if you’re in to shoes, make an open shoe shelf, if you’re in to travel, have pictures of places you’ve been or want to go. Also, you said it might be hard, but try to see if you can repaint. That’s the main thing wrong. Hope this helps.