ok so my GF and i are both 15 and have been going out for 9 months now. we started out as really good friends until i asked her out and she said yes she liked me cause i was "sweet and funny". we sometimes go to each others house and she almost always wants to cuddle on the couch she says im her " big cuddly teddy bear". she also likes to sit on my lap and she likes it when i carry her on my arms. anyway im 5'8 and 255 pounds so i know i am fat, but i am perfectly happy with who i am. and shes not fat at all she is a small girl shes 5'0 and im going to guess around 100 pounds, and she is super gorgeous. we sometimes playfully tease eachother about our size like i will tease about how short she is and she will tease about my weight but we both have high self asteem and we know were just kidding. we kind of have like a Doug and Carrie relationship (from the show King of Queens). the only thing im curious about is when ever we hug and kiss she likes to grab on to and hold my fat rolls and love handles like last weekend when us and a group of friends went to the beach (we live in L.A btw) and beleive me she looked hot in that bikini and i went with swimming trunks and my shirt off i though oh she is not gonna like what she sees but i was wrong she lit up when she saw me and we hugged and kissed and she did the same thing grab on to the rolls and love handles, also while we cuddle she likes to squeeze and rub my belly. really dont care that shes doing this. if anything i like that she does that feels good i guess. i guess im just curious. her past BF have been averaged sized, or muscular 6 pack guys im like her first big bf. and btw with her past BF they have only lasted only a few weeks but they were all jerks so i understand why they didnt last and like i said we have been dating for 9 months.
again dont get me wrong im not complaining im just curious

It sounds like a combination of two things. One, she is in love with you. Two, maybe she just likes thicker guys. There is such a thing as girls like healthier boys.
I personally like a guy that is either muscular, or a little chunky, preferably both. I know a lot of girls like this too.
The only real way to know is to ask her, but to me it sounds like she loves you and is attracted to you, and perhaps thats her way of showing her affection
Best wishes