Period29 days late!

Hey everyone. I had a pregnancy test done a couple weeks ago at my doctors office and the blood and urine were both negative. I have NEVER been this late before. The day I was suppose to start my period I just had brown stringy discharge when I wiped but nothing else. That lasted for 2-3 days then stopped. I am type one diabetic, controlled, not under a lot of stress. But I’m just wondering if this has ever happened to anyone else. I have symptoms of pregnancy but tests are negative. I haven’t taken one in a couple weeks but do you guys think I could be and just not making a lot of hormones?? Doc says if I don’t have a period this month I’ll need to go in for further testing. We have been TTC for 4 years. With one miscarriage last year