Bites on baby

Hi everyone, can anyone identify what bites are these? For the past 2 months my baby has been getting these random blisters on his arms And legs. We went to see a Paediatrician and she gave us creams medication saying it was some kind of bug bite. After which it did heal. But last night, my baby woke up crying and I only realised his swollen leg with these blisters. Just to let you know he sleeps on a mattress next to me (sometimes I will sleep w him on his mattress and his mattress is new) and he wears long sleeve and long pants to sleep as well. I haven’t gotten any bites, has anyone experienced this before and how do I stop them?