Pregnancy symptoms?

My husband and I are trying to get pregnant, but due to still breastfeeding my son, my cycles aren't at all consistent. I'm "timing" the best I can, and if I'm guessing right, then I'd be about 1 week pregnant. I didn't think much of it until this morning when I woke up with a bad case of hives that have been going on all day. I haven't eaten or done anything differently and was wondering if anyone else had hives at about a week pregnant. I have been pregnant once before and don't remember anything like that (although I didn't realize I was pregnant until about 8 weeks along and could've just not noticed). Thanks in advace and serious answers only please!