Normally, a person doesn't go to an ER for fatigue. Did you go because of the rapid heart beat and numbness? If so, they likely did heart and stroke evaluations. The bloodwork for those would not have included thyroid testing.
You have many of the symptoms that can be related to thyroid disease, and you must have tests specifically for that to find out for sure. The minimum tests you need are TSH, free T4, free T3, and thyroid antibodies.
Be warned that many primary doctors might not take your complaints seriously, because you are male and young. Many ignorant practioners will tell you that thyroid disease is a "woman's" thing. Politely insist upon the tests you need, for no other reason than to rule out thyroid trouble and move on to the other possibilities.
"We can complain because rose bushes have thorns, or rejoice because thorn bushes have roses." Abraham Lincoln