If it feels good for you, it is probably good. The warnings are about the sleeping position, which is unnatural (meaning your body wasn’t built for it) and may lead to pain, joint ache, breathing problems etc.

However, laying on your back can be a huge relief for your back, I know that from experience. Especially if your lower back hurts, it’s a very good way to work against the painm but I guess your reading position is also different to a sleeping position, your neck is bend upwards and also you push your back more through.

Laying on the stomach can also help with stomach pain and ingestion problems.

In the end everybody is different. Carefully listen to your body and how it responds.

Also I can really recommend going to the gym and strengthen your torso, especially back and stomach muscles. I feel so much better than before, I think I can never go back to not working out.