Don't pull one ear out.. the whole purpose of IEM's is to have BOTH in. If it bothers you, turn down your OWN vocal level in the mix.. I do that because if my vocal is too loud, I tend not to sing as hard and higher notes will "crack".It's really off-putting hearing to much "me"!
I also have the other vocalists level lower than mine (barely there, so I can hear him when he's talking to the audience) because listening to him (+ lead vox in 3-part harmonies) at too high a level, will often throw me off. I only put kick/snare in my ears.. don't care about toms, and I don't monitor lead vox's acoustic. He doesn't start any songs, or solo, so no need for it.
I 'm telling you this because you may need to experiment with levels to see what works for you. I had to, but I gig regularly so it didn't take long.
Whatever those may be for you, you should NOT have to pull one ear out when singing...