John-
If you're new to shooting, be aware that most competitive traget shooters wear double ear protection. In-ear plugs are combined with the big ear-covering insulators for more protection. Note, also, that the latter are available with electronic cutoff circuits that will allow normal noises through (like conversation) and block harmful ones (like gunshots).
With respect to your sound problem, I'd look to your choice of speakers. There's been recent talk about Schroeder cabinets and how they improve cut-through of the bass. Smaller drivers pointed at your head will probably help you hear yourself better. I believe you have to get a fair bit away from the 18s before the sound comes together. That kind of tone is a double-edged sword, because you don't hear it well standing close, but it can overwhelm your bandmate across the stage, so he turns his amp up louder.
If you just love the way the 18s sound to the audience, then you might want to try adding a small bass monitor system to your package. Heck, you'r already carrying 2 18s, what's another cabinet? Something with 10(s) or 12(s) that can point at your head and cut through without having a major affect on what the audience hears. Otherwise, you might look at replacing one of your 18s with a cabinet based on 10s or 12s. There's a lot of great stuff out there right now, and a cabinet with smaller drivers stacked on top of the 1x18 should make a difference for you.