I am 21 yrs old..I have been suffering lately(since 25 Dec '10) from this sharp pain at left side of my belly button, characterised by frequent pains that leads to frequent visits to bathroom. My stool appears to be "acidic" accompanied by froth. Previously , I was having just weakness all over, but now it has changed to pain in my vulnerable joints. My back pains quite a lot,even the sides of my abdomen(esp the right side), my left knee,my left ankle is swollen from yesterday.These pains are just "weakness pains",and so in good parts of the day i appear perfectly fine.