What could be causing my urine to smell bad?

I am a pretty healthy, fairly active 22 yr old female & the past few months I've noticed my pee smells pretty bad. In other words, differen than it used to. I'm not trying to be gross or weird, it's just the facts. Be mature, people. If you cant handle it, answer someone else's question. Anyway, back in August, I had had a urine sample done at my yearly physical exam & that didn't raise alarm for concern. It came back normal. Is it something to be concerned about? or do I just need to eat better or exercise more etc? I do not have any health problems that I know of (other than being diagnosed in 2004 with Crohn's diesease, an irritable bowel sydrome). Any advice/tips appreciated! Thanks.