negative tests can be wrong. Positive tests are rarely wrong.

U can try again. If the test comes out negative, it could be because your hcg hormones may be low (if pregnant) and is not detectable. Sometimes if you leave the test long enough, they can detect faint "positive". But usually 6-8 weeks pregnant hcg levels would be high enough to determine if positive or not. Usually quite instant.

If your test comes out negative BUT you still suspect pregnant. (got all symptoms of being pregnant, nausea, tender breasts, etc) then go doctor do vaginal ultrasound. They can detect the heartbeat is any at 6-8 weeks. Then congrats!

If your test comes out negative, and there is no symptoms of being pregnant and doctor said NOT pregnant, then you are NOT pregnant.

Not having period doesn't equate to being pregnant. Not having period could be due to numerous factors. Hormones, Stress, cysts, prolypes, polycystic ovary syndrome, eating disorders, etc etc.

Speak to your gynea and express your concerns. If your gynea doesn't give you the care and attention you need, find another gynea that gives you the information you need. they can advise you best on how to proceed.

Some people don't get their periods for a few months at a time.
It's not normal but it happens and they are not pregnant. Ask your gynea everything under the sun that you can think off that is worrying you until you are satisfied. cause you paid for his/her services and expertise already so you might be clear about what is happening to your wife.