Hi there and welcome. Well, I'd take another home pregnancy test. Those are pretty reliable these days. Hormones with pregnancy increase day to day to day and those tests register if that hormone is present. You have to have the hormone to be pregnant and it has to increase to sustain a pregnancy. So, an at home test should be able to pick up the hormone. I bought early detection tests with my pregnancies and got positives when I tested before my period was due. (the tests say you can use them 4 days before your period is due and that is what I did and got positives. Faint lines but positives none the less).
Now, as far as symptoms, well . . . those are because of the hormones. Again, these hormones increase over time and that is why most women have VERY few symptoms right away. Nausea or morning sickness starts on average of week 6 to 7 for women (which that was 100% accurate for me).
So, take a test to determine if you are pregnant and go from there. I do want to mention that often we can just have a really messed up cycle too. I was having periods that were spread 2 to 3 months apart with major pms during that time. It was due to a hormonal issue.
So, test and then if it is again negative, make an appointment with your doctor. good luck
You might want to go get a blood test at the doctor's, pregnancy test are not always accurate. It could also just be a change in your menstral cycle, i know with me sometimes ill get mine 3 or 4 days before the expected date. But its best to go get checked because you wouldn't wanna wait and it might be something worse.