Hi, I Am A 25 Y/O F, I Have Reciently

Hi, I am a 25 Y/O F, I have reciently gone into the ER twice in the last week for tachycardia and heart palpitations, had EKG done, and was told it was SVT but the episodes have not stopped, i have a history of depression and anxiety that started a few years ago, as well as rapid weight loss and a hard time gaining weight, consultly fatigued, and a new onset of a short menstral cycle, and tremors on top of the constant elevated HR, the ER did do blood work, which showed mostly normal lab values other than an elevated lymphocytes of 56% they said they checked my thyroid, but they only checked my TSH which was at a 1.99, no T3 or a T4, I have a family history of thyroid problems and have a feeling I may have one myself, but every doctor I have seen had brushed it off as anxiety attacks, and I am at a loss as to where to turn next!