I have a 7 month old pug who has always been the sweetest, most loving little dog. About one month ago, I noticed that she would start growling viciously when I would go to pick her up (whereas before she would be so excited and happy to be held). Once she would be put down, she would start turning circles round and round as if she was chasing her tail. I took her to the vet. After MANY tests and x-rays, they found nothing. I've noticed this aggressive behavior becoming more frequent, but not so much with strangers. She is friendly and playful towards people she doesn't know. I wondered if this behavior could have anything to do with her getting ready to come into "heat"? This is definitely not the precious, sweet little dog we've been living with since September. Help!!!