Why does this always happen? is it ALL about getting laid?

First of all it will not last. You seem like you may be a bit of a challenge and have some self respect. Girls that are easy are just that, they are easy! It is a chance to dip in it and duck out, pardon how I am putting it. The guys will talk about her and what they did with her and how easy it was with her, and so on. You already know you do not want yourself in the same section as her. You need to just keep being you, hold your head high too. For most boys at a young age and many times into their twenties it is all about getting laid. Half the time they can not help it. It is the hormones and the level of maturity that they have. At least you know what kind of boy he is, and you know to stay clear of him now. I am sure much better things will come along for you. Good Luck!!