Irregular periods. Or kindly advise!

Hi,I'm 25 old.Till now i had never faced Irregular periods.On April 1st week i had Sexualy connected with my partner. But No Intercourses happened between us.Don't know if slightly has.For sure intercourses not happened.On April 29th I had my Period With Dark colour But Bleeding lasts for only 2days and later completely stopped. On May 30th It was just only 4-5 Drops of blood for whole day. Later drop kind of blood stopped and Period has not happened in may and there is no symptoms as well.Even i have done pregrency test in the Morning for twice in prega news,The result is negative. Today is 35th day But Still there is no periods happened and there is no symptoms as well.I can just feel very slight back pain and dizziness.i have ate pappaya as well to get but no periods happening. From last one year, I'm working in night shift but never faced irregular periods.Till now I have not even taken any pills as well. I'm so worried. Is there any tablet to get the periods or Kindly Advise