from the sounds of this you are not ready for a puppy..honestly you would be better off with an adult.. puppies are like children, they need attention and love to stay happy, they also need somthing to do or they are going to have tons of energy stored up and start becoming destructive...Have you talked to her breeder? A good breeder should always be there for you and your pup to awnser any and all questions you might have. You have to remember she is only 11 weeks old, still very young, shes going to chew shes going to jump, because she does not know better...whenever she is chewing on somthing she isnt supposed to take it away from her and replace it with a toy that shes alowed to chew on, and praise her whenever shes chewing on one of her toys...whenever she is jumping up on you say "off" and GENTLY push her off of you...as you already know brittanys are working dogs, they need to be both mentally and physically stimulated..somthing that will keep her busy is a toy called a "roll a treat"..as she pushes the ball around a treat will randomly come out, heres a site that sells them..
http://www.pettoysplus.com/index.asp...ROD&ProdID=312
You NEED to put her in puppy classes, yes it can become expensive but it is a must..as she grows bigger and older you will be happy that you did...honestly if you dont think you can give her your all, it would be in her best intrest to give her back to her breeder..
good luck, and just remember to be patient, puppies are going to be puppies..keep us updated on her progress