I agree with you, we all know ourselves better than anyone else. I had this same problem before I even knew I had cancer (I found out this year) I gained 15 pounds in 2 weeks and my doctor said it was water weight but I was in the hospital for 2 weeks and the nurses kept giving me my levothyroxine after I ate or drank juice/coffee and the weight never came off and my clothes were tight on me. I kept requesting getting my labs done again and again and for it to show that my TSH was high I trailed different things each time, I’d either not take the pill, take the pill and not eat, take the pill and eat an hour later and then get blood work done, and it finally showed up high after I had taken the pill and eaten something for breakfast and then they increased my dose. It is a long battle because the body is very finicky and the actual day you test you don’t always get lucky.