Signs of Pregnancy but negative on test?

For preference i am a healthy and healthy weight 18 year old girl starting 2 new jobs and in school full time. I am about 10 days late for my period but when i have taken MULTIPLE pregnancy tests they all came out negative. I have had occasional cramps, nausea, tender breasts, low weight gain, and some food cravings but still, negatives on all tests that i take. I’ve tried different brands and different kinds of tests but with the same result. This happened to me back in February the same way for THREE MONTHS then the period magically came back. My doctor couldn’t explain it. I haven’t taken my birth control in over a month now. Can someone explain? I’m out of answers and I set up an appointment with the Woman’s Center on Thursday.