This is not a disease at all. What you are talking about is an ingrown hair.
I would recommend not shaving down there and maybe get women;s clippers instead. I have used that for over 10 yrs and have never gotten an ingrown hair again.
I understand what you are feeling because they are painful to say the least.
Hi and welcome. i would say its all from shaving. Instead of shaving these sensitive areas, try letting it grow back and just trim it. Really its not natural to shave this area. The hair folicals are getting irritated from the razor and what ever soap or cream your using.