With my boyfriend of 3 years, we just moved in together recently. but now when ever he kisses me i've broken out into hives. this has never happened. ?

Food allergy?: If you are allergic to a food and your BF had recently eaten it, then his saliva can transmit the food to you. Having been together for 3 years, it is unlikely that excitement was the cause. See allergist if the problem persists.

Rare: You may have become allergic to a protein in his saliva. You might, less likely, be allergic to something he eats every day but you never eat. Or an allergy to some medicine or herb that he takes. Try a daily antihistamine such as ceterizine (Zyrtec)------not Benadryl (diphenhydramine). Probably you will need to part ways so you can each find somebody to safely kiss. An allergist might help you.