If you aren't taking thyroid hormone, you should be.
Your FT4 is lower than that of a person without thyroid problems. If your FT3 were tested, it would likely be too low also.
The fact that your gland is enlarged means it's struggling to keep up with your hormone needs. Yes, you could say it failing.
Is your doctor receptive to prescribing meds for you? If not, you ought to get another opinion or three... whatever it takes for you to get what your body isn't providing for you.