What Causes Soreness Around Hip?

I am very active and run about 20km a day 6-7 days a week, with strength training on top of that. Recently (in last couple of months) i have noticed my right side round my hip (when you push in under the bone) is really sore. it sometimes feels swollen on both sides but pain is mostly on right side. I have had two kids, youngest is 18months and have not had my period since falling pregnant with 2nd child. Also always have a bloated gut every evening. Not sure what it is or what causes it?