The reason for having palpitation
and feel loss of energy is sign of Hyperthyroidism
. This can be due to increased thyroxin levels in blood. While advising medicines for thyroid gland it has to be regularly monitored by checking thyroid profile to check the effect of thyroid drugs. Sometime they still can't bring the thyroid work normally or sometimes overshoot. But there is nothing to worry. You just need to decrease your dosage under your physician guidance and everything will be ok.