Is my female Papillon about to go into heat (for the first time)?

my female pap is about 8 months old (born 6-24-10). she has not yet gone into heat (no bleeding) and from reading i don't think she can be pregnant b4 the bleeding. lately she has been very sleepy, and cuddly (like right now, she is sleeping in my lap at the computer desk), when she normally goes and lays in her designated areas to sleep. she is also getting very whiny, and is always wanting my attention and affection, more frequently then normal. OH, and shes also been shedding a ton lately, and its the dead of winter (snowing outside). are these signs of pre-heat? i read that their nipples get bigger and their vulva becomes slightly swollen, but to me, they look the same. , any advice or word of wisdom would be appreciated??