What Causes Red Welts And Swelling On Feet?

Last Saturday I was bitten by something whilst on holiday in Bali. I had loads of what I thought were bites but as the days went on, the red welts spread, and swell up periodically (and then subside). I have been to the doctors and been given chlorpheniramine (I'm 26 weeks pregnant). I started taking this on Wednesday - 4mg on Wed and then 8mg yesterday. So far, I'm not really finding it is helping that much and I'm continuing to get new red welts on my feet as of this morning. What would your advice be? Thanks