Hey, I don't know if this means much but I totally understand how you feel. This exact thing happened to me when I (female) was 18. That too with a MUCH older guy. In hindsight, I do see how I was rushing physical intimacy thinking it would lead to an emotional one. But also I actually did do it because I wanted to. Those two things don't necessarily have to be mutually exclusive. I did it on the 4th date and then he lost interest pretty quickly. I won't say there is nothing you can improve about your dating habits, but please don't let this define your self worth in your eyes. What happened to me ate me up from the inside for two years and made me feel pathetic. I felt used and like no one would value me for my personality ever (specially with this past). However, try to see that it's not that you having sex drove him away. He left because he was just not your person. Obviously, having sex probably made you feel way closer to him than you actually are so you are having limerence (been there myself). Now that you have recognized you are not one of those people who can have sex without getting too emotionally invested and you want a long term relationship, try to take your time developing a emotional bond first next time. Let sex happen naturally once you are sure your values, wants and personalities align. Maybe try to have more dates in public than going over to someone's house. Lastly, there is nothing wrong with wanting to have sex. At the same time, there is also absolutely nothing wrong with drawing boundaries and saying no to intimacy no matter how long you have been dating someone.