Well, a lot of things in human sexuality are "normal," though the technology angle is probably a relatively new twist. You don't say how old you are or if your activity is interfering with your normal life. If this seems to be interfering with normal life, it might be something like a sexual addiction. If you are underage, it might be something you should limit for your own emotional safety (and your safety from the dark side of sexual things for young girls too, such as inappropriate involvements with men who care about only their own sexual gratification). To stay strictly with your question, it's normal to get excited and easier sometimes with your own imagination than with another person. To counter the feeling that it is somehow excessive, try doing things that you like and give you a sense of yourself as competent and giving. Work on being a well-rounded person and sexuality will take its proper place.
It depends. How old are you, and how old is this "boy?"
I'm going to tackle another part of this post. Sending explicit pictures of yourself ito another individual is not normal and is a VERY bad idea.
1) You dont know who will end up seeing those pictures - are you aware that photos on a phone can be sent uploaded onto a computer very easily? Before you know it, these pictures of you could be circulating all over the web.
2) You don't mention how old you and your bf are. That being said, it is possible one of you could be considered in possesion of child porn which is illegal.
peek -- I hope she's not 12 too. Equally, I hope she's not one of those weekend posters we sometimes get.
spade -- excellent point about the Internet-upload capacity of these pix. Sheez.