Ummm, pretty much if a guy is talking regularly to a girl, he'll desire her for sex. Now the difference is if he wants to just get laid, or if he's really into the girl. If he's into you, then he'll put in the effort to show that he genuinely cares for you, will commit to a relationship with you.
Guys who are using a woman for sex often give few or no details about themselves. Have you gleaned what you know about him from friends, personal observation, general conversations, past interactions, or has he really volunteered personal and revelatory information about himself to you? This is a very telling point, so it is worth considering carefully.
A sign is the Booty calls , so 12 o'clock at night to 1or 2 o'clock in the morning calling or texting about sex and only sex and in almost every conversation throughout the day just so happens to end up on the topic of sex somehow and he doesn't in introduce you to any of his friend or family like you and him being together or talking is a secret like on the DL.