I'm having upper back pains whenver im in bed and my back is very tight and wont pop anymore. Could it be a muscle strain? Or something else?

Muscle first but. I agree. We thinkof muscle first but your evaluation will need to clarify why this occurs when you lie down. There may be other causes and yor evalauiton will clarify this.
Back sprain. Back sprain is very common and can be seen after heavy lifting, exercise or sometimes lying in bed in certain positions. I would recommend position changes. Range of motion exercises at home can help as well in addition to anti-inflammatories such as ibuprofen, Motrin or advil.