I finally find a girl that is what I want: A Formal relationship, this girl cares for me, she loves... She already presented me to her family... I know her brothers already, I was playing XBox with them.. I am 19 years old, and I have wanted a relationship where I would get to know the family and spend time with them, and here it is !!
Buuuut... I keep focusing a lot on her physical appearance ... she's probably an 8 or 9 from the face, but she has a little extra pounds, I mean, she is not fat, and she takes care of herself, maybe it was the holiday parties, shes going to the gym as soon as she enters school ... But why do I have to let that small flaw in her physical appearance make me doubt!!

Do you represent a healthy lifestyle?
If so , you can just pull her into your lifestyle."Hey ! How are you ? Listen , I have planned to go jogging on saturday and I just can't stop thinking about whether you could keep up with me or not ? '
Invite her to some sport game or anything to show her that you're into healthy lifestyle.Normally she will get the hints and start to exerice.

Well thats an issue within yourself to solve.
Just ask yourself why your with her and how she makes you feel when your with her.

If not, and youd much rather her slimmer, above comment sounds good. Be careful though, girls overanalyse gestures and situations all the time. She might catch on to what your trying to do and take offence to it.

Keep it casual and sublte when your asking her to exercise

That sounds like a good idea...
I was taking to her right now and I said something like
"I gotta do exercise and prepare for summer"
And she said something like
"Yeah me too, skirts time"
Then I went ...
"Lets get really fit " And she responded "Yes"

So, at least she has it in mind, not like other girls who wouldn't think it ...
Its not that I'm superficial, or anything, but I really think about introducing her to my friends, and well, at least have them say "Oh shes hot..."
One time I introduced a girl I was dating and a friend of mine (A girl friend) said.. "I thought you only dated models" ...
And since then I've been really picky on that :S

I think you figured it out. Good Job....... !! You know your mistake and thats the first Step.