Extreme Tiredness, Anxiety, Have Constant Hives, Swelling In Throat After Delivery. Had Overactive Thyroid Before Pregnancy That Normalized With Pregnancy. Is It Resurfacing?

Hi before i fell pregnant with my son ( 4 months) i receieved blood tests that showed i had an overactive thyroid . Anyway during my pregnancy the levels returned to normal. However since birth ive started to feel extremely tired, anxiety is through the roof, pulse & bp are all over the place, im suffering constant hives , a swelling in my throat that comes & goes each day. Aprox 6 weeks ago my gp put me on citlopram for the anxiety which 2 hours later triggered what they think was a severe allergic reaction & since then ive had hives every single day ( for 6 weeks) & feel extremely poorly. There is thyroid problems in my family & im wondering is this thyroid problems & is there a possibilty now im not pregnant that it could be back again. And can it cause symptoms similar to allergic reactions. I also suffer from vitaligo which at the present moment has become active again.