How do you deal with mixed messages?

First of all, I don't deal with mixed messages because I interpret them as a game and I don't tolerate games. Second of all it's clear as day that he's using you for sex. He's getting his jollies and sending you on your way. Whether he likes you or not is irrelevant at this point. What you should be asking yourself is, does he respect me?

Ok first off. Why are you having sex with someone that you don't think likes you? You need to have more respect for yourself. Also, I don't think the signals are mixed here. He is getting what he wants out of you without having to give you anything. If you really want to know what's going on with him then you need to cutoff the sex and talk to him

Not sure the messages are that mixed here. You don't even know if this guy likes you, but you let him drop by for sex whenever he feels like it? Are you doing this because you think this relationship has long term potential? (Seems unlikely. ) Because you want to help this guy recover from his depression? (Again, seems unlikely. ) Some other reason? Dunno, but seems to me that you are letting this guy use you for sex, on his terms. Is that really what you want to be doing at this point? Is this likely to end up in a good place for you? If not, you probably want to think about ending this, sooner rather than later. That's my advice, for whatever it is worth.

These kind of "friends with benefits" (which is what it is since you are not boyfriend/girlfriend) relationships are great until one person feels more attachment than the other.
Often, girls enjoy the emotion of sex and guys enjoy the physical release.
To be blunt, he's gettin' his rocks off with you when he needs to, so why ask for more problems by trying to build a relationship?
If he was/is depressed, hopefully he got help to get him out of the situation. If not, you may be enabling this booty-call-based relationship. However, if you and he both agree that this works for you, it may not be "mixed messages" it may be just the inability or lack of desire to commit to a real relationship.