Choc: Ive seen the rounded shoulders and protruding neck of both those with a fondness for the bench press and other variations of upper body pushing movements as well as seeing this in people who *ahem* sit behind a computer for several hours a day.
The rounded shoulders and protruding neck which can be stressful and cause headaches as well as the conditions you described. It often is the case of overactive pectorial and anterior deltoid muscles as well as over stretched/underactive mid lower trapeziods and deep cervical flexors.
Simple answer, do a whole lot more pulling movements than pushing movements. Rows, and lots of variations of them but yet again, your form has to be correct. If you are compensating in your form then you may further aggravate the condition. Something that is kind of hard to do without someone there to give you verbal cues and act as your visual aid.
One thing that often helps me when it comes to keeping that back square during these types of movements is to think of the back side as a kite where the strings are attached on the back side of each shoulder as well as in the middle. These strings are all being pulled taunt into one line....an image that usually places me back into correct alignment when in question. Obviously core strength is in place here too but more than that, it is important to concentrate training on the entire posterior chain, (backside) from the traps,rhomboids,lats,posterior delts,multifidius, glutes,hamstrings,calves...bascially the entire backside from top to bottom.
This link might also include a few more details for you. But basically, pull more than you push right now and you should be able to develop better posture to help support the weight you carry in the front with less pain.