There are several conditions that might effect menstrual flow and cause spotting. Aside from pregnancy, you could be having a hormonal imbalance, along with a number of other possible causes. Certain factors such as stress, anxiety,diet etc, can also play a key role in mentrual changes. The accuracy of a pregnancy test is usually pretty good, however, if you are still unsure, you should consider getting a medical evaluation to rule out your direct causes.
I hope this information may be helpful, I wish you well & Thank you.
