What Causes A Fluttering Sensation In The Chest?

About 4 months ago, I went to the emergency room thinking I had something wrong with my heart. My blood pressure went up over 200. All my heart tests came out good. The doctor said my thyroid was not working. I had a strong fluttering in the heart, a feeling of something squeezing my arms and chest, pressure on my eyes, dry skin, hair falling out pains in my hand, weakness in my hands, a gravely voice, extreme coldness. tiredness, and can never lose weight. I was prescribed a low dose of levothyroxine. The first few weeks of taking it I felt great, then things started returning back as I felt before only with more muscle pain in my shoulder area. After taking the levothyroxine for 3 months, my blood test on T4 can out normal. I am still taking the levothyroxine. Is it possible that the hormone is not being utilized in my body or that I may be allergic to the medicine? I am only taking a .05MG of the levothyroxine. I have read that it can also cause the same symptons that hypothyroidism causes. Is that true?