Haven't gotten my period but been light spotting for 3 months im not on bc & p test r negative I have had sex 3 times since nov?

See a doctor. Home pregnancy tests are very reliable, so it is unlikely (though not impossible) you are pregnant if you are reading the results correctly. Regardless, you should visit your doctor to determine the cause of your missed periods. If you are not wanting to be pregnant you should discuss birth control which will also help with cycle control.
Need Exam and Labs. I think it is best to get an exam and labs to get to the bottom of the problem. This is a great question but it requires more than a quick reply from us over the internet. Hope this helps.