Possibly pregnant after 3 negative tests?

I'm really nervous that I may be pregnant even though if I was I would be 14 weeks right now and I have taken 3 tests they have all said negative but I'm also having some gastric problems so I cant eat much and I don't really have an appetite and I've had periods every month since after I could have gotten pregnant but the flow is light then really heavy then light then medium and it lasts like 5 days so I don't know if that's normal either I'd really appreciate some help because my anxiety is starting to get the best of me