Brief Answer:
Yes, it could be reliable

Detailed Answer:
Hello,
I'm Dr. Branch, thanks for using 'Ask A Doctor' service.

The most common cause of a false negative (meaning, the test is negative but actually there is a pregnancy) is testing too early. Pregnancy tests test for the human chorionic gonadotropin, which usually becomes detectable by 2 weeks after conception, certainly by weeks 3-4. So at 7 weeks, it would be plenty of time for the hormone to become detectable.

There are a few other causes of false negative pregnancy tests which have to do with the technical aspects of the test, but they are very rare and do not need to be considered unless there is some other evidence that you are pregnant.

So in your case, I would consider your result to be very reliable and conclusive that you are not pregnant.

I hope that helps...
Please let me know if you have any further questions...
I would be glad to discuss it with you further.
Regards

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