Did anyone check your iron and ferritin (iron stores)? I see your profile lists you as a male, but it is possible if you have some GI bleeding you may not even know about (occult/hidden blood in stools) or an absorption problem for males to become iron deficient. A person can experience symptoms from this iron deficiency, even if their CBC is not yet affected- it happened to me. One of the symptoms of iron deficiency can be rapid heart rate. Another is poor concentration. So, if you haven't gotten at least your ferritin checked, you might ask the doctor for that test.
Also, you say your EKG was abnormal- was it abnormal in that it demostrated sinus tachycardia, supraventricular tachycardia or ?
Tingling can come from peripheral neuropathy, poor circulation, and even as a result of a panic attack. You might ask for doppler testing to see if you might have peripheral vascular disease, which can be hereditary and can strike even as early as teenage years.
Poor concentration I believe is common with anxiety. Also, some people eat less, while others eat more with anxiety. Weight loss could be from anxiety, but I believe it could also come from a rapid heart rate itself- like you are getting a work-out of sorts without having to exercise.
I was diagnosed with inappropriate sinus tachycardia before having a tilt table test, where an electrophysiologist diagnosed me with postural orthostatic tachycardia syndrome. Both are forms of dysautonomia (see community forum on medhelp), dysfunctions of the autonomic nervous system.
In case you are having anxiety, you might try something like vitamin B 50 time release to see if it helps any, deep breathing exercises, listening to enjoyable music, getting out and enjoying nature, doing relaxing hobbies or serving others in volunteer work, and if you are a Christian, prayer.
You might want to work on lowering your cholesterol naturally, by diet and excercise and get re-tested to see if your cholesterol has gone into normal range. Steps like:
Exercise to increase your HDL, which fights the LDL.
Things like butter spread with plant sterols for lowering cholesterol, pistachios, which can help lower your bad cholesterol, getting enough omega 3 fatty acids (which can be found in things like many nuts such as macadamias, pumpkin seeds and freshwater fish).
And lowering sugar intake to help with triglycerides.