Do I need another new retainer after new permanent crown fell out and was re-cemented or root canl?

Permanent crown on tooth18 on 12/21, no root canal, decay under existing crown, deep cavity. Impression/new retainer made at Ortho 12/22. Crown came off on 12/28, extremely sensitive & re-cemented 12/29. Fine until a week ago. No sensitivity or pain when chewing but noticed jaw pain (subtle) and throbbing (crown) especially when wearing retainer (p.m.). New retainer has always felt like it fits so why now?Xray yesterday showed no sign of infection, also no sensitivity or pain when tapped on.