Thyroid function continues to decline

After having my second child 33 years ago, I began taking 1 mg of Synthroid, diagnosis of hypothryoidism. In recent months, my thyroid level has continued to decline. My Internist has completed full blood tests to confirm, adjusting med from 1mg to .88 and now, .75. Can anyone tell me what might be going on with these numbers? I have recently had an endoscopy, results were gastritis....stress ulcers. My cholesterol is too high, taking Lipitor 3X weekly. I have hypertension and am taking med for this as of 2010. I really wish I could get some answers as to what might be going on. Can anyone assist with your viewpoint? Three years into retirement and I should be feeling awesome, right?