Can sex make disc herniation worse?

Sometimes: Any activity that increases intra-abdominal pressure (tightening of the stomach muscles) will increase the pressure on the disc and thus pinch a nerve harder. This can be uncomfortable until the symptoms of the herniated disc resolve.

Not commonly: Avoid being placed in uncomfortable or awkward positions (including hyperflexion at the waist/hips), make sure you are in a comfortable position during sex.