Hives Only At Night

It's been 16 months since I had my daughter , and 3 months after having her I broke out in hives almost every night and I still do , at first I thought bed bugs but I've had professionals check and I'm all clear also I'm the only one who gets them my husband doesn't and it only happens at night, I use the same detergent that i use on my clothes as well and I never break out during the day. I don't know if it's a pregnancy thing but anyone else ever had this happen?