This is not a normal way to feel.
And yet a huge amount of mothers have admitted on this thread that they feel it. I imagine there's thousands upon thousands who do. So while it may not be pleasant i think it actually is "normal" considering the sacrifices mothers have to make (and it really is mothers for the most part which is the crux of the issue).
One could argue that's it's really not "normal" to love being a mother. Considering the barbarity of the birth process, the pain, suffering, sacrifice, sleep deprivation, episiotomies, stitches, ripped, torn and stretched bodies, listening to screaming, crying, tantrums, loss of identity, loss of autonomy, loss of financial independence, loss of time for hobbies, interests, friends, societal pressure to be an "earth mother", impact on your relationship etc etc. obviously it won't be this way for every woman but for many that's the reality.
Instead of the lovey dovey aspects of motherhood we're bombarded with (by advertising etc.) imagine we were fed the above notions and were told we had to do all the above while pretending to be happy about it and to never, ever show otherwise least we be ostracized as social pariahs? It would take a special kind of masochist to willingly sign up to that shit!