My lip piercing is randomly becoming swollen!?

So I have my lip pierced. I've had it pierced since November of 2010. I haven't any problems with it until now. For the past week its been really sore and has become swollen. I have cleaned it, changed lip rings. I have a hoop in. That's the only kind of lip ring I can wear. To clean it I have used sean salt and warm water and it's just getting worse. I really don't want to have to take it out. So I need help!