If you're experiencing back pain while doing core exercises, it's important to be careful and listen to your body. Back pain during exercise can be a sign of improper form, muscle imbalances, or underlying injuries, so it's important to address the issue before continuing with your workout routine. I would recommend speaking with a medical professional such as a physical therapist or a doctor to get an assessment of your back pain. They can help you identify the cause of your pain and recommend appropriate exercises and modifications to help you build core strength safely. In the meantime, you can try modifying your core exercises to reduce strain on your back. For example, instead of doing full planks, you can try doing modified planks by resting on your forearms and knees instead of your hands and toes. You can also try doing exercises that target the core muscles in a seated or standing position, such as seated Russian twists or standing cable rotations. Remember, it's important to prioritize safety and listen to your body when it comes to exercise. Don't push through pain or discomfort, and always seek guidance from a medical professional if you're experiencing any issues.