This was my exact problem 2 years ago. Vague aching pain, sometimes sharp, on the right side of my ribcage. I avoided going to the doc for 2 months but it didn't go away. Finally made an appointment and he said he "wasn't impressed," but ordered an ultrasound anyway. The ultrasound was clear, I started probiotics (have had IBS for decades) and it finally went away. Just another weird thing with my body. But I'll bet it's something digestive. Things moving too quickly/slowly can cause pain.