Scratching my scalp and eating whatever comes out from under my fingernails

I super sensitive skin so sometimes my scalp gets irritated and make little bumps on my head. I have got in the habit of scratching my head every single night as a sort of ritual. I do it so often that there is always some sort of scabbing and I scratch them off along with just dead skin and the bumps themselves. making more damage. I then will scrap it all out from under my nails. I then will eat whatever comes out from under them, Scabs, pus, dead skin, etc... 

Sometimes this is the end of it, but more often then not in shifts to picking at other part. Bumps on my arms and leg. Sometimes my face. I just want to be able to have a night time routine, but if I try and do any sort of skincare, it leads to me picking my face like crazy. 

I have been doing the route of having acrylic nails on, but I have stupid nails that even if everything is done perfect. Buffed right, primed well, applied well, but my nails just pop off after a week or so... its so annoying and expensive. 

Does anyone know a good way that even if you scratch you dont do damage, of at least a whole lot less than before? I really want to kick this habit. Its bad. my brain knows this, but it feels like muscle memory at this point. Help!