How do I tell if my situationship actually likes me or if he's just using me?

So I've been talking with this guy for about 3 almost 4 months now, we've consistently been each other's number 1 best friend on Snapchat for several weeks now and anytime I snap him he snaps back almost instantly (unless he's at work then obviously it takes him longer).
He normally doesn't start a conversation with me, I'm normally the one to start it, but he always seems very interested and not just brushing it off when we are talking.
When we're hanging out he's very talkative and sometimes picks on me but it's also mutual. If I really like someone I tend to pick on them as well, playfully of course. We have fucked once or twice if that matters, but we don't get often bc we both still live with our parents so figuring that out is a bit weird.
Please help! I need answers!
How do I tell if my situationship actually likes me or if he's just using me?
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