My hair has been thinning out gradually over the past 4-5 years (I am 26 currently), with follicle density and hair thickness both reducing. Recently shaved my head and discovered that I haven’t been thinning as evenly as I thought, I actually have a ton of these tiny patches that are more thin/bald than other parts. You can see my scalp is almost entirely covered in a dotted pattern.
This could be a condition called diffuse alopecia areata or a fungal disease. See a dermatologist who may biopsy one of these patches.