When you had your thyroid checked, did they check the Free T3 and Free T4 or just the T3 and T4. They are completely different tests and unless you ask most docs will run the standard T3 and T4 and not the Free's. You can have normal labs and if they run the Free's they may be at the bottom of the range indicating a thyroid issue.
If you are having low thyroid symptoms I would insist on checking the Free's. That was how my thyroid issue was finally diagnosed after 3 long years of misery thanks to ignorant doctors.
As far as the cholesterol issue during the time that I felt I was hypo I kept having high cholesterol around 230 and I am slim and had been on the candida diet for 15 months and couldn't figure it out. After a few months on thyroid meds my cholesterol dropped to 140 so it was the thyroid issue affecting my levels.