As the saying goes, anything under the sun can cause urticaria
. If you are able to find out the cause its well and good.
Since you say its almost 4 weeks now and you are on medications, please check if you have some hidden infections like urinary infection/ dental caries
etc as hidden infections can keep producing urticarial rashes.
If you are breastfeeding
, tell your doctor so that he can give you the medicines safe during lactation
Hope you find my answer useful