I play a few chords using my thumb. For example, for D I put my thumb across the second fret, minus the last (A) string. For E I do the same on 4th fret, and put my index finger on fret 2, last string. I also use my thumb on B and some other chords besides. Although I've been doing this for over 2 years (which is how long I've been playing), I still feel like I'm "cheating", if that makes sense.
Anyways, does anyone else besides me use their thumb in this way? Is it bad practice?