My period is 16 days late, 3 home pregnacy test have been negative can i still be pregnant? i have thyroid problems but am on medication for it

Yes: Some types of pregnancy do not result enough hormone to show up on urine pregnancy tests. You may need a blood test, or in rare cases, the urine test may become positive, with a normal pregnancy. The question is whether there is a chance you could be pregnant, especially whether there's been unprotected sex within the 6 weeks. See your PCP to make sure.