Paniculata hydrangeas, including ‘Pee Gee,’ bloom on new wood, meaning you prune them in spring just before new growth begins or thereabouts. They can be cut back quite hard, and still make new wood that then gets buds and blooms, but it is too late now for this season I’d say. I have had ones I didn’t cut back enough turn to octopuses (octopi?) and really look a mess, and this is inclined to happen on older specimens that have been cut back again and again. At some point you have all these knobby places where you’ve cut back to each year that are sprouting too many stems in every direction…and you have to cut a little farther next time. That said, I do sometimes go back in around late spring or early summer and take out a few of the worst offenders among the shoots of new wood, leaving some of the better-placed ones. Hard to see without seeing your specific plant, but perhaps this will help a bit? Compared to most other shrubs I find H. paniculata a little hard to prune since I have trouble imagining where the new growth will sprout and which direction it will go in (again, especially on old plants). So you are not alone!