My dermaroller is not working

I started derma rolling for 3 months and stopped maybe two months ago. The needles are 0.5mm long.  My hair has just got much worse and thinner and i don’t necessarily attribute that to derma rolling but i have done research and seen people saying it can cause scarring. I used a 0.5mm derma roller once every two weeks maybe once a week a few times, is there any chance from this i have caused scarring or damaged hair follicles and would I know if I had caused an infection because that’s another fear of mine, thanks

The scalp has two layers; the top layer is the epidermis, and it is mostly avascular. It measures 0.5mm thick. The next layer down is the dermis. The dermis contains the stem cells and hair follicles you must reach with the microneedlng. With 0.5mm length, you are doing little to help yourself. Set up a routine, use something like the Dr. Pen device, and go down to 1.25mm. Cover each area you want hair to grow for 10 seconds. Then, move it to the next place. Most people seem to do it once a week, which works. If you keep everything clean, wash your hair before you start the microneedling and then later wash it off with another good shower, the infection risk is low.  Good luck