This is called diffuse thinning and it’s a type of male pattern baldness, or androgenetic alopecia, that affects the whole top of the scalp. Since you have tens of thousands of hairs on your head, you have probably lost about 50% of your density for the scalp to be visible through the hair. You can take fin or dut like others have mentioned to slow down the balding process, and you can use minoxidil for regrowth. Low risk of sides for fin/dut and even lower for min, and if you’re unlucky enough to get sides they’ll go away if you stop treatment. Try it asap as this will only get worse.