I'm 20 years old and I'm starting to date after a 3 year relationship. I met this guy and he's really great I like him, we recently started having sex and now his whole attitude changed towards me. It's like he's only interested in having sex he won't text me anymore, and the other day he left my house and went to hang out with another girl he didn't let me know i just saw it on snapchat. I really want him to want to get to know me more. We always have great chemistry when we are together but it's like the second he leaves he forgets about me. Did I mess up a chance of a relationship with him because we started having sex already?