No period iud

My preiod is 11 days late ive had iud for 18 months now since.having iud my periods have been regular and light im concerned as my period is never.this late ive took tests but.all negative. I am worried as when i fell pregnant with my second.i was.testing for 3 weeks before.a postive showed on test so im thinking i am pregnant what do.i do just hope.period comes or keep testing my gp says they.wont do anything unless test.is. positive but.have said its.normal not to.get.a period when have iud but 18 months having it i thought.periods.would stop at 6.to 12 months