Had a similiar problem and came about after my 1st and only punt. Was a rub and tug,and at the time i put it down to the oil used. In fact it wasnt, then out it down to shower gels and being sensitive to them. Went doctors numerous times,and eventually told to goto sti clinic.
Popped along had numerous tests,all negstive after being asked some pretty personal questions. 15 minute wait and told all negative. They put it down to ballonitis, and was given a cream witch did help somewhat. Now its cleared i have realised it flairs whenever i eat wheat, ive have a wheat intolerance i.e gluten. Im fine now,but occasionally on weekends i let myself go,few largers maybe some sandwichs and yorkshire pudding on roast on sunday my body flairs up.
Im not saying you have a gluten intolerance,but for me thats whatit turns out what it ended up being. Now im gluten free 95% and the weekend i let.my hair down,but i soon stop as the next day i get itchy bollox and bloat up and instop eating it.