During pregnancy, it is common for the abdominal muscles to tighten and the uterus to expand, causing the tummy to feel hard. This can be due to Braxton Hicks contractions or the baby's movements. It is usually not a cause for concern unless accompanied by pain or other symptoms. To alleviate discomfort, try changing positions, practicing relaxation techniques, staying hydrated, and avoiding strenuous activities. If you are concerned or experiencing severe pain, consult your healthcare provider for further evaluation and guidance.