Is it normal that my ex boyfriend only liked me because of my boobs?

It's normal when the guy's a little douche bag and only interested in one thing. But, now that you know you need to take some responsibility and accept that you, I and most everyone trains others on how to treat us based on what personal boundaries we set with them. In the future I would highly recommend that you take your time and be certain of the nature of the relationship you're in with another person before you sleep with that person.