The cheapest (and I think most effective) option is to mix up some rock salt and warm/hot water in a cup, bend over it, press it to your belly button to create suction, then stand back up. Do some crazy swishy-belly dancing to really flush out the wound, then bend back over and release the cup. Do that twice a day and that's how I used to clear up my belly button infections

Don't take your piercing out if you can help it - I did for the last few weeks of pregnancy and my hole closed up! I managed to repierce it to earring-guage and now only have a thin gold sleeper in there :/ a bit of a let down. It got terribly stretched and scarred though in my last pregnancy and I'm now 31wks again and it's stretched to the limit.