It makes a difference as the spleen is on the left, appendix,
gallbladder and liver are on the right.
Appendicitis can hurt on the right lower quadrant or right around the belly button. Your gallbladder can hurt below the ribs on the right and the pain can go through to the back and up to the shoulder. Can be intense or uncomfortable.
If the pain is on the left and your spleen is affected, it could be a symptom of Mono.
At any rate, you need to see your doctor.