Yes, it is completely normal for your baby to be constantly moving and doing flips in your stomach at 5 1/2 months. As your baby grows, they have more space to move around and explore their surroundings. This movement is a sign of a healthy and active baby. However, it can sometimes make it difficult for you to sleep at night. To help alleviate discomfort, try changing positions or using pillows for support. If you have any concerns about the intensity or frequency of your baby's movements, consult with your healthcare provider for reassurance and guidance.