u have allergic reaction
known as URTICARIA
u are taking right medicine i think it is anti histaminic .
it is safe and effective drug
as u develop it 2 day after stopping drug means u have very low allergy
u need to find out the cause
it may be due to some food ,drink ,pollution etc
u can go for allergic sensitivity test also
u should do CBC ,THYROID
TEST AND SUGAR TEST .