170 lb 5'5" f. L5 Spondylolysis and facet syndrome dx in sept. Feeling a slight bump on spine, is it starting to slip? 4-6 on px scale always.

Not likely. Not terribly likely, but you are right a spondylolysis can sometimes progress to a spondylolisthesis in which one vertebrae slips forward on the other. I would not hesitate to be seen for an X-ray if you are concerned, particularly if you are having increased pain; but it is pretty uncommon for that to happen.