Is he being a jerk or does he really like me?

Unfortunately yes, some asshole guys (and a few girls too) will do that. A good litmus test for that trait is typically the people they hang out with - i.e. their friends. If you know their friends are assholes, they usually are an asshole at heart as well.

As for your very obvious self-esteem issue. What you refer to as "beautiful" is only your perception. This guy's previous girlfriends may have been physically attractive, but were really ugly people on the inside. It is possible that this guy is looking for a personality over a Barbie world girl, you never know. The best advice I could give you would be to actually confront him about it. Confront him about it with a little attitude built up, so that you come across as being pissed off. If you confront him (especially in front of your friends with some of his friends around), it is likely he will be honest with you about his true intentions. His response may be painful, and he could just lie to your face(s) to ward off any ridicule from his asshole friends, but either way, you will know for sure how he feels about you or, at least what you should do about it. If he denies liking you, ask him why he keeps inviting you to his games when his friends aren't around. Basically, just embarrass him. If he really does like you, but is too embarrassed to be seen with you, he is not worth the time of day anyway - he's too weak.

If you are concerned that nobody finds you attractive because of your being overweight, then you have only two choices. Lose weight or stop thinking you are unattractive because you think you are overweight. "Overweight" is also a perception. Anorexia patients think they are "overweight", while everyone else thinks they are too skinny and actually look like they are sick and malnourished. What you consider "overweight" may be considered too skinny for others. There are thousands of websites specifically targeted to people who like overweight people. There are "Chubby Chasers" all over the planet. The bigger the better. But, there are millions and millions more websites dedicated to people whose tastes run to a more height/weight proportionate look. If you are not height and weight proportionate, your chances of finding a guy are unfortunately significantly reduced, but gather hope, because there are quite a few who relish the thought of dating BBW (Big Beautiful Women). Don't believe me? Check out Craigslist.org and search BBW. You will see most personal posted ads will request that BBW do not apply, but a few will specifically request the company of them. If you are a BBW, my best advice would be to see a nutritionist and lose the weight. While you are young, it is significantly easier (with faster results too!) to lose weight. Besides, the health problems associated with obesity can really screw up the rest of your life, and according to your profile, that is a long time. Good luck.