How do you know if you have ?

last week I noticed a bump appearing over my lip on one side and thought it was just acne, but later on it scabbed over white and there was some pus. then i got rid of it and it reappeared i think. now there is only a little white on it and it is barely scabbing over. i looked on the inside of my mouth today and noticed a white bumpy skin peice on my inner cheek, and then realized it goes on to be a whole little line... what is wrong with me!? does this happen after giving a bj?