Didn't you ask your doctor?any number of things can postpone your period. Stress,medication,ect. How old r u ? Pregnancy tests r pretty accurate. Talk to you doctor!
Sometimes that happens to me when Im so stressed out or really worried. I would just relax if i were you. You have like 5 tests that came out negative. Its fine. Just relax. Being nervous about it wont help at all
If your young, your period dosnt regulate untill you have had them for acouple of years.
I was the same with this untill i reached 18.
If you have had negitive test there shouldnt be much to worry about.
If you have more concerns maybe.see your doctor :)