There are many reasons why some women may have
pregnancy symptoms even when they are not pregnant. The most common reason is because of
hormonal fluctuations that can happen randomly, especially around the time of your expected period. This could sometimes also be the reason for a delayed period. In general, this doesn't last very long, and in a few days or so, you will have your period, and then the symptoms will resolve.
If the symptoms last for several weeks, and you are still not pregnant and still don't have your period, then you may need to ask your doctor to check hormone levels such as
prolactin and
thyroid hormone, which can be related.
It is also possible that you are pregnant, and that you are too early for the tests to be positive. If that was the case, then in a week or two, if you still don't have your period, you can check a pregnancy test again and it should be positive. I hope this helps, if you need any more information, please feel free to ask me.