Thanks for writing here.
Your description and case history point towards perianal infection.
It can be due to ingrown hair.
Continue sitting,ferquent travelling.wearing tight clothes can cause such conditions.
Use loose cotton undergarments.
Take sitz bath which can give soothing effect.
You need to take oral antibiotics
and pain killers for relief.
At times such infections can form pilonidal sinus
which needs to be treated surgically.
Hope this will help you.Take care.