My Abdomen On Right Side Where The Ribs End Is

My abdomen on right side where the ribs end is tender to touch and can feel it through to back. There is a wierd discomfort when not pressing on it. Movement doesnt really seem to effect it. It is very worrisome to me as I have never felt this before. I took my temperature it was 99.7. I dont really feel like its an emergency should I wait to see if it passes or go ahead and go to an ER. It started today. I am 29 and female last cycle started November 26. Im at a lost to what could be causing this.