Can you get lock jaw more than once?

Yes. Yes, since the locking jaw (either jaw dislocation or disk dysfunction) is a chronic problem. Complex problem. see a TMJ expert for guidance. Any dentist can be a TMJ expert with the proper training and experience. Most commonly, oral surgeons, prosthodontists, and orofacial pain specialists. Ask your MD, your dentist and your dental society for referrals.
?tetanus ?TMJ. Do you really mean lock jaw as in tetanus? Or do you mean your jaw locks as in TMJ (jaw problems)? It is rare to get tetanus twice unless one is not keeping up with the tetanus shots every ten years and is in an occupation/hobby which exposes one to tetanus. On the other hand, if one has TMJ problems, the jaw can lock up on multiple occasions. In this case, see a TMJ physical therapist or doctor.
Yes. Tetanus is produced by toxins secreted by clostridium tetani. The amount of toxin necessary to produce clinical disease is far less than the amount necessary to induce immunity, so any patient recovering from tetanus should receive tetanus immunization before discharge, or they may well reacquire this disease. "immune" patients may get it if the toxin produced is quite high and the immunity low.