@dinnerlady , unfortunately, your GP has been too dismissive.
You should contact your MS Nurse to discuss these issues. You should then be referred to Continence Services, who should investigate the causes. Usually, it is urine retention, something which is quickly confirmed by an ultrasound.
You maybe offered anticholinergics, to calm your bladder down. You may also be offered Intermittent Self-Catheterisation (ISC).
ISC may sound an awful solution, but it guarantees an empty bladder, which may then allow an undisturbed night’s sleep!