Why not start by posting your thyroid related blood work, so we can see where you're at, right now... there may be a reason for you to be going up and down. You should be getting tested for Free T3, Free T4 and the inevitable TSH. Don't forget to include reference ranges, as those vary lab to lab and have to come from your own lab report.
Do you know if you have Hashimoto's?
I can't imagine where you would have read that coconut oil causes heart problems, as it's very good for you...
Coconut oil is a superfood.