You know, the idea that there's something wrong with someone having a lot of sexual desire comes form the stigmatization of sexuality. There's nothing wrong with being someone with a lot of sexual desire, a little sexual desire, no sexual desire at all, or being somewhere in the middle of any of those. Same goes for someone who has sex -- alone or with others -- a lot, never, a little, what have you.
However you are in this respect, it's all good. And what your personality is isn't something this tells us much about. Our personality is who we are as whole people, not how often we masturbate, one super-tiny detail in a whole life and whole person.
"Horndog" usually doesn't just mean someone who wants sex a lot, the connotation I feel like I hear it most carrying is as someone who does, but who also is shitty in their pursuit of that with others, or some other negative. If that word makes you feel crummy, throw it out.
What's too much masturbation really varies from person to person, and how often doesn't really tell us what's too much. Instead, you'll want to think about things like:
• Is it keeping you from other things you need to do?
• Is it keeping you from other things you want to do?
• Is it having a negative impact on your relationships, including with yourself?
• Are you injuring or otherwise harming yourself in any way (like by rubbing your skin raw)?
How do you feel when it comes to your masturbation and those questions?
Never doubt that a small group of thoughtful, committed citizens can change the world. Indeed, it is the only thing that ever has. - Margaret Mead