A couple thoughts:
1) With a background in powerlifting (even half-assed powerlifting a few years ago), you are likely well positioned to make some strength gains quickly.
2) One theme in my time bouncing around these forums is that, until you are approaching pretty high levels, the specifics of programming are much less important than consistency and effort. There are a bunch of really strong guys bouncing around these forums, and no two of them train exactly the same.
3) With that said, it sounds like you're kinda lost right now. You're doing a 5x5 program, but you also recently joined a CrossFit gym. I have some issues with CrossFit, but I also admit that they create a fun/competitive atmosphere which works really well for a lot of people and they emphasize barbell lifts along with gymnastic movements and overall athleticism. I'm a pretty self-motivated guy and I'm little too stubborn to just show up and do whatever the CF coach recommends, since it may be contrary to some of my personal preferences and goals. However, in your situation - struggling a bit with motivation, uncertain what to do next - it might benefit you to go ahead and just do the CrossFit box's group programming for a few weeks, then decide if you're all-in CrossFit or if you want to shape your own programming, possibly incorporating things that you liked from CF.
4) Whichever direction you go (full-on CrossFit, fully self-coached, or a hybrid of the two) there's one critical thing in your post:
Biggest issue right here is to get in the gym regularly, put in some effort, and believe in what you're doing. That doesn't mean every workout has to be a killer. Most of mine really aren't; four or five days per week I'm in the gym just "punching the clock" or "building the base" with a real breakthrough workout that seems to come along every week or three.