International insurance number? Guess you mean National Insurance Number.
What your husband has said is total rubbish.
You don't need to get a National Insurance Number to apply for jobs, it's actually ok if you only arrange a National Insurance Number as soon as you start work or gt a job offer.
You definitely do not need a National Insurance Number to register with a doctor. My wife actually registered with my doctor before we married and as she wasn't allowed to work she couldn't get a National Insurance Number.