Pain in the back

3 days ago, all of a sudden, right before I went to bed, when I got up from my chair, I felt a stinging pain in my lower back. I didn't care so much and slept. Next morning I found it a bit hard to get up on the bed because of the pain. It got worse toward evening until I felt hard to sit long at the desk. Typing on the keyboard is especially hard because I have to lean forward to do it. So most of the day I lay on the bed reading books.
Now I felt a little better today and am writing this. I have gotten similar acute back pain a couple of times but this time I feel it longer to get better... Getting old.