Irregular periods here and then.

I do have irregular periods since my first menstrual cycle..but every time I consulted doctor..I m with only answer hormonal imbalanc..quiet common due to stress etc...do exercise..some medice for 5 days and tonic that's it ..noelw I m married 6 mnths ago...everytime my period got irregular I m expecting pregnancy...last time I do experienced spotting..andbi googled it...and went for a pregnancy test..I m  disappointed..with negative result and same medicine...this time too..it hadbeen 60 days..I dnt got my period...I do have severe back ache..mild cramps in abdomen..sore breasts..etc ...but with home pregnancy test I got negative...wat would be the main reason...I m worried..for my pregnancy .please help me in sorting out...give me set of conclusion wat and wen should have my tests to make myself confident...