If the rash comes immediately it’s possible that it’s just a result of very sensitive skin, but if it lasts that long it’s unlikely. It’s probably a condition called folliculitis, which is very common. It’s an infection of staphlococcus from the skin that gets into the openings caused by pulling out hairs. To fix it you can try these steps:
Use a new razor every time if shaving, and try not to use the razor from the infected parts of your body on other parts.
Use a topical antibiotic (batracin) every time you tweeze/shave, etc.
Wash well with an antimicrobial soap when you shower; dry off well afterwards.
If this doesn’t help after a month or two, then you might want to see a doctor and get a prescription for an antistaphlococcal antibiotic. This should kill any bugs in your system already, and hopefully reduce the chance of reinfection from the skin. Not all antibiotics are antistaphlococcal, so be sure the one you take is.
Hope that helps!