So the basic answer to your question is home pregnancy tests are most reliable at 7 days after a missed period. So, based upon that you are a bit early to have a conclusive negative test. Positive tests can surface sooner than that, but for a negative test to be reliable - 7 days. A blood pregnancy test would be accurate now, however, so if you didn't want to wait another 4 or 5 days you could explore that avenue.
Now, it is not uncommon for a woman to be late or even miss a period - a woman's hormonal system is very sensitive and can easily be disrupted by stress, anxiety, hormonal imbalance, illness, thyroid problems, medications...etc.
In other words, pregnancy is not the only reason to be late or miss a period. Additionally, when this happens (and pregnancy is not the culprit) there is a hormonal imbalance to some degree that causes the other symptoms - such as moodiness, breast tenderness, bloating, etc.
So in closing - it's too early to say you are not pregnant. You need to repeat a home pregnancy test in 4 or 5 days with the first void of the day as that's when the pregnancy hormone is most concentrated and will yield the best results. If it's positive, you are pregnant. If it's negative I'm comfortable saying you are not pregnant and this is likely just a hormonal imbalance from one of the things I mentioned previously. Typically, this resolves on its own with time and menstruation begins on its own. If, however, you miss 3 periods in a row you should talk with your doctor about medication to start your period.