So i'm 8 days late. i have been getting headaches, back aches, cramping, and recently started taking synthroid (thyroxine) ? am i pregnant or is it the medicine?

Trust the test : Home pregnancy tests are very accurate. They are the same tests used in a doctors office. They can detect a pregnancy 7-10 days after conception. If you doubt the result you can repeat it in 1-2 days. If you were pregnant the hormone level would rise enough for detection. Cycle irregularity is not surprising at 45 years old. There are many options for cycle control.