Oh dear, I totally understand how uncomfortable that can feel, especially when you are trying to rest at night, baby tends to be more active when we slow down and lie still, so we notice the movements much more then. The position baby is in could be why you feel it more on the right side, and those little kicks and stretches against your ribs can really be quite sore! Since you are already 28 weeks and the rib pain is bothering you, it would be good to mention it to your doctor or midwife at your next visit, just so they can check baby's position and make sure everything is well for you both.