Fingertips burning/skin going dark

I have been using an iPhone X for over 2 years. A few months ago my right index fingertip would become uncomfortable and I wouldn’t be able to use that particular finger after a minute or so of scrolling. The screen felt like it was burning my finger and would cause a sharp pain. This slowly became the case with every finger over time as I’d always switch fingers. With the fingers I use the most the fingertips have turned dark. I thought the phone was faulty so I got a new IPhone XR and the same thing is happening. I can’t use the phone without a stylus. I’ve been to the doctors twice and even had a test for carpal tunnel syndrome (I don’t have it). I don’t know what is going on, I don’t think it’s EM Sensitivity because I don’t seem to have a problem with my HP laptop. Can someone please help me because I work within social media and my fingers cavy take this anymore. Thanks in advance.