Welcome and thanks for the query
As you have done UPT twice and you are 14 days overdue with negative reports so you are less likely to be pregnant.To be on safer side get an ultrasound
done which can explain the cause of delayed periods like PCOD
etc.Weakness and delayed periods can be due to anemia
also so get your Hb level done.Get thyroid profile done as hypothyroidism
can also cause delayed periods.For all these investigations it is better to see your doctor.
Best wishes and take care