Hives?!

My husband and I are TTC and I am about 6 days from when my period is supposed to start (a little too early to test, I tried this morning...negative). I am trying not to symptom spot but I am having crazy cramps, nausea, and peeing all of the time. Yesterday afternoon I developed hives all over my right arm, by dinner they were on both legs. Has anyone experienced this before? Is this something that I should be worried about? Any and all insight appreciated!