I have this exact pain too and the same daily occurance. It gets worse in the evenings or after I eat.
My doctor said that he believes that it is postural-related. The pain hurts in the front of my rib cage, but it originate from your back. You need to sit up straight and pull your shoulders back. Stay active and stretch your arms and chest several times a day. I did prenatal yoga and the arms and chest stretches we do help me the most with this pain. Also, when its hurting really bad, I will do pelvic tilts and this helps too. I do a modified verson of the pelvic tilt at work, when im sitting in my chair. I tuck my tailbone under and lengthen my spine and tighten my ab muscles and hold and try to take deep breaths. Then I keep the position but bend to each side. Usually, if i bend over on the right side, the pain will stop, but my instinct is the bend backward to ease the pain, to stretch the area our, but that never helps.
Also, reduce the amount of fat you are consuming in your meals and eat smaller portions, this will help with the pain spike after meals.
I have a sit down sedentary job, so I am stuck at my desk alot. I recommend if you have to do that same, to get a balance ball and sit on that at your desk instead of a regular chair. This makes you sit up straight and helps with posture and strengthens your ab muscles. This makes my pain far less severe when i use my exercise ball. Even if you just use it a few hours a day. the change up helps. Get up and walk around and maybe do a few yoga moves on your break.