Hello and welcome to Healthcare Magic. Thanks for your query.
It is rare and unlikely that a urine pregnancy
test cannot detect a viable pregnancy even after 8 weeks. So, it is most likely your hypothyroidism
which is resulting in the missed periods. The only way to be sure about this and also to rule out the rare possibility of an ectopic pregnancy is to have an ultrasound
scan done. I presume that your gynecologist will be doing this in case you still don't get your period.
Dr. Sheeba Stephen