Recently(4 weeks)i developed a pop/click sensation posterior to my sternum. i don't think its joint related as it occurs irregularly w/ mild inspiratio?

May be rib: Many ribs attach to the sternum. Although not your typical joint they still have the potential to get inflamed and have some movement, which could happen with inspiration. The rib could also have a problem posteriorly where it comes off the spine but you would feel the symptoms anterior. If this is the cause a provider who is skilled in adjustments can be very helpful.

Costochondritis: Sounds like costochondritis. In this condition there is inflammation of the cartilage at the junction of the ribs and sternum. It is often painful. Nsaids are usually helpful.