Hi ! Possibly you are developing a right inguinal hernia
. This is protrusion of abdominal contents like omentum or parts of intestine through a weak opening in the lower abdominal wall. When you went to the doctor, it might have reduced of its own, and so the doctor might not have felt it. This will be prominent whenever you do some work which increases your intra abdominal pressure. For this you may have to get yourself examined clinically by a surgeon.
A simple cyst
will remain there always and will not go away in between.
One more possibility could be a hydrocele
of the cord, which may behave in the same way as a hernia if communicating with the abdomen.
I would suggest you to consult a general surgeon
to exclude any of these possibilities.
Wishing you an early recovery.