What's going on with this?!?

Okay, so about 20 minutes ago, my legs,arms,back,stomach,feet, and hands started itching really bad. All of a sudden, I had hives. I know you usually get hives if you're allergic to something. I'm allergic to ragweed,pigweed,hickory trees, hard maple trees, and cats. Yes that's a lot isn't it?lol. But the weeds & trees r outside, and there's no cats in the house. So what else could be causing this? I know it's not the laundry detergant or shampoo or body wash, because ive been using the same kind all the time. I've broken out in hives AT LEAST 6 times within the last 20 days. I need answeres please. I don't wanna go to the doctor, cause the hives will probably be gone by the time i go there anyways.