lab starting to cry

Question
My lab is 9 months and she is only now starting to cry alot during the day. We go for long walks everyday and she gets to play with other dogs and run freely at the lake, but when we come home she sleeps for a while and then starts to cry and keeps on walking with me to all the rooms and stands up when I stand up, as if she is ready to go and follows me in the house.Could there be a problem like she is not feeling well?

Answer
If she hasn't been spayed, you can expect all sorts of behavior changes as her first season approaches.  If she hasn't been spayed, I would talk the vet now.  You may be able to still get it done before going through the risks, mess, and hassle of of a female in season.  

If you are thinking of breeding her, please do some reading.  http://www.woodhavenlabs.com/articles.html#breeding is a good place to start.