I was wonderring if you've called and gotten checked out. As others said, it could be anything from normal aches and pains to a problem, its not something wwe could even really guess at,you need to get checked by your doc and most likely have an echo or other test.
Altho "Usually" if pain is new several weeks post op or gets alot worse like yours seems to have, it probably wouldnt be just the normal pain from having your chest open etc. but everyone is different
Also it is often said IF you over do, this close to surgery, your body will not be happy and let you know it, so it could just be from going to the wedding less than 3 weeks post op, if you stayed too long.
Your wife is right, it is really important to work on good posture post OHS, even tho it can be sore to stand upright, its one of the things you have to work on, or you can make other things like your back muscles hurt. Are you working on everything you should have been told to do when you started your recovery, getting all your walks in, working on your breathing exercises thru out the day or anything else they told you to do? They might not seem like they help, but the breathing really helps getting your lungs to expand, loosen up tight muscles etc. and really help with recovery.
ps. Im not sure it is the best ting to put a graphic OR icture in the middle of a thread since you can't really warn people who might not want to see pictures lie that before or even after their surgery, so they cant reading the thread.