Swollan painfull stomach?

For the last 2days my stomach as become really swollan and painful even when i bend down or move around.Ive also got lower back pain.This has come after having a strange monthly period which was very light very dark coloured and thicker than normal(not a liquid).I contacted my GP he told me 2wait untill my next monthly period. It is a very small chance i could be pregnant im on the pill and havent missed taking one for months. What r ur thoughts?