I play church gigs every weekend, and can hear myself very well all the time. There is a learning curve, but the most important thing is; If you can't hear yourself, you don't start by turning yourself up. You start by turning other things down. If you can hear yourself OK when noone else is playing, then your signal is fine, stop trying to adjust your gear - you just need to learn to mix (or ask for what you need for a good mix), starting with what I just said.
A good IEM mix does NOT include everything on stage at equal levels. You need pitch and timing references. Kick, snare, hi hat - those are your timing references most of the time. Some (but not a lot) of the guitars and keys in your mix help with pitch reference. But the thing (besides your bass) that you need to hear above all else is the voice of the person singing lead. Background singers, reverb, other effects that make it nice for the audience and singers - those should be turned completely off. You need to hear what is important for doing your job, which may not be the "nicest" mix. Once you have what you need, everything else is just stuff that gets in the way.
This last weekend (It was Easter, we pulled out all the stops) we had a 30 voice choir, a half a dozen strings, a couple woodwinds - in addition to the usual rock band complement - 2 electrics, one acoustic, keys, drums, and bass. The amount of choir and orchestral instruments I had in my in ear mix? zero - I didn't need them to do my job, and not having them in my mix made the things I did need to hear that much clearer.