unexplained pircing infection

I got my belly pirced four years agoand before last week it had only gotten infected once because a cat hair got into it. Well last week i wnt to bed one night and the next morning it was infected. now i cant evern weatr my ring without it getting worse and now its closing. ive tried cleaning it but all i want to know is what could cause the infection.

[shortyvms]

You could have become sensitve to the nickle in the jewelry.  That happened to me.  Everytime I wore earings my ears became infected.  Now I wear nickle free jewelry.  No problems.  Put some hydrogen peroxide on the affected area an then put some neosporine, might help it clear up.  I also sometimes dip the earring hook or post in neosporine sometime helps to prevent an infection.  Hope this helps.  Good luck.