You should probably prepare for bad news. The tree shows signs of bacterial canker infection which is reinforced by your description of the onset of the problem. The infection enters through cuts, blossoms and tools used to prune. It is made more likely in areas with a cold climate not tempered by the proximity of large bodies of water. It can affect cherries and peach and apricot and particularly the latter which is more affected by cold and is more susceptible.
Outward signs are raised rough black lesions on an otherwise smooth bark, blossoms that fall off prematurely, and sudden death of what yesterday appeared to be perfectly vibrant shoots. The first two may not be visible, but the last is. The infection is spreading inside the tree from the top down, killing the sap transportation tissues.
The tree may try to send up new shoots from low down on the trunk where the tissues are still good, and may even send up water shoots from a rootstock, but eventually the tree does not grow at all. It probably means that your location is too harsh for tender apricots.
By all means get other opinions, but consider removing the tree as soon as possible, your neighbours might consider it a source of infection and start mumbling, and wait years before trying a stone fruit tree again. I'm sorry, this is the worst, I know. Consider maybe an apple tree, which is hardier?