I have been getting a lot of sharp pain in my rib cage lately, from the area of my diaphragm, almost to my collarbone. I began about 3 weeks ago on the right side, but now it is happens all over my rib cage at any time of the day and I get split-second twinges for up to 45 minutes. I was thinking it could be asthma related, or possibly due to bad posture and tight muscles. I have never had this problem before.
No, asthma wouldn't cause this kind of pain, nor would bad posture.
Pain radiating up to the shoulder area, like this, could be referred pain from something irritating the diaphragm. It is best to be seen so we can sort it out.