Yes, you have to get to know yourself and fine-tune your meds until you see where you feel most comfortable. It's very much a trial-and-error process. Symptoms are of the utmost importance every step along the way.
Most of us start out taking T4-only meds (Synthroid, etc.). In my opinion, until FT4 is approximately midrange, T4 should be increased. At that point, if symptoms remain, supplementation with T3 meds is indicated if FT3 remains too low. FT3 and FT4 levels should be balanced for complete symptom relief. If symptoms still remain with good FT3 and FT4 levels, it's time to try dessicated...some people only feel well on this - synthetics don't work for them. Of course, this is just one path. Some are adamant about taking dessicated right from the beginning. It's very much personal preference for them. There are advantages and disafvantages to both synthetics (IF they work for you) and dessicated. You should read arguments on both sides of the issue before deciding. If any of these tell you that only one or the other works for everybody, stop reading and go on to the next opinion.
How do people come to learn they need a different med, or to have T3, or to go natural? Also, is it just paying attention to your symptoms that you learn what targets are best for you?
We are all different, so there's no set answer. It takes at least 5-6 weeks before you get the full effect of the med, but it can take much longer before you actually "get well".
I've been on med for right at 2 yrs and it's just been in the past few months that I've felt anything like my old self. That said, there were a few things that I noticed "improvement" on in a very short time.
Can you post the results of your latest blood tests, along with the reference ranges on your lab report.
Be sure that you and your doctor pay greater attention to your symptoms than to your #'s and treat accordingly.