toy chi/yorkie

My female dog is about 1 years old and I am not sure if she has gone through heat yet. Today she is acting more different than usual. She is breathing a little heavier, not eating or drinking much, not jumping, just want to lay down, she yelps if someone tries to pick her up around her belly, her vagina looks bigger, her tits look bigger, her belly is tight, and she curls her bottom in if you go near it. Any advise.