If a 3-and-a-half-month-old baby has not had a bowel movement in over 7 days, and appears to be straining and stiffening multiple times a day without any results, there are some steps you can take. You can try increasing the frequency of feedings and performing exercises that can help the baby pass gas and feel better. These exercises include massaging the baby's belly in a clockwise direction while lying on their back, doing bicycle movements with their legs while lying on their stomach, and having skin-to-skin contact. These actions may help alleviate any discomfort the baby is experiencing.