18DPO negative test

I’m TTC I have been since may my periods have always been regular but this month I’m 18 DPO and my period is 4 days late which is unusual. I did have spotting at 7DPO and pulling and feeling full in my lower stomach. Today I took a test it came back negative I used clear blue digital and a boots cheap test should I be using different tests? My symptoms today are breasts are sore and swollen, I have heartburn which I never have, I keep having hot flushes and dizziness and I’m constantly tired. I’m going insane here has anyone else experienced anything like this?