An ill-fitting bra can cause various issues. Signs include: 1. Red Marks: Indentations or red marks from straps or bands indicate tightness. 2. Spillage: Breast tissue spilling out of the cups suggests the need for a larger cup size. 3. Riding Up: If the band rides up the back, it may be too large or too loose. 4. Discomfort: Any form of pain or discomfort is a clear sign that the bra does not fit properly.