Do Irregular Periods Cause Negative HPT Inspite Of Being Pregnant?

Okay so here is my question , my periods just started becoming abnormal . and starting last month i have been getting abdominal cramps , nausea , hot sweats or flashes , constipation , and a milky discharge with no smell . I have taken about 6 pregnanct tests all negative but for 3 weeks or so these symptoms have been coming . I was told , not sure if its true , but that irregular periods can cause a negative HPT or something like that due to the hormones being imbalanced . im not sure i just need help . also i did bleed in march on the 19th for 3 days could that have been the implantation bleeding ? if so then my last NORMAL period was feb.28th , 2011 thanks for your help .