You need to speak to a nurse,doctor or chemist for further advice. They will talk to you in confidence- (without telling anyone) and even the chemist will speak to you in private if you wish.
You need to find out what is causing the symptoms if you are not pregnant and if you are then the sooner you know the better.
Do not let people on the internet advise you on something that is this important to you. There are rare occasions when these tests are not accurate. But if the test result is correct something else is making you have these symptoms - so seek professional advice. Good luck Lianne - I hope all works out well for you.