Trust your DOCTOR !or trust yourself ??

I am 28 going on 29. I started my period when I was 11 years young. I had my.first child at 17 and my second at 25. I have always , ALWAYS , always started on the 28-30th day ... sometimes sooner . Never later. My last period was 3/11/16 . April came and I had brownish spotting... but nothing like my previous years of periods. I have gone to a doctor ... who only.did a urine test and said it was negitive. However, my last baby took weeks before a positive . I'm 53 days since last my last period ... no blood. Just weird cramps in my left side ..... doctor said ...we can trick our minds into having/not having a period. However, if that was accurate ... my period would continuously be off , we've been trying so hard for 2 years! Help