It sounds more like your tree is a Weeping Higan cherry. The Kwanzan is an upright tree. There is a new weeping tree called 'Weeping extraordinaire', the info says it has "Kwanzan like" flowers, but it has not been released as yet. Every search I have made for Weeping Kwanzan shows the tree as being of up-right vase-like growth.
http://portlandnursery.com/pla...
http://homeguides.sfgate.com/d...
https://ask.extension.org/ques...
A location of where the tree is, and pictures of your tree would go a long way in helping to discover the problem.
