No such thing as fake crying. Babies young children have very limited ability to communicate a need. Crying always indicates a need regardless of age. Are they hungry? Cold? Overly tired. At 4mth they need sensory like toys, music, soft stuff to touch, prsctice grabbing stuff. Or they might like having mommy near them because it makes them feel safe. Remember babies can't provide anything for themselves. if you need a break try some safe floor time or tummy time with some black and white cards.