Guy's Behavior

He says he wants to keep it casual, so why is he acting like a boyfriend?

he usually texts me good morning, talk on the phone or text a lot, hang out a lot, and wants to hangout with my friends when i go out with them. we also joked about going on a vacation with each other. he told a mutual friend of ours that its just casual between us. but we have been messing around sexually and yesterday we were sitting with each other and talking about cars and he said that he found it hard to sit near me because he wants to kiss me. i also joke around with my friends that there's a baseball player i have a crush on and am excited to go a game soon and he made a comment about it and our mutual friend whispered that he's jealous. another friend of mine said he sounds insecure but I don't know why.

previous convo of ours was lets keep things casual and if we decide we want something more than we can talk about it.

Updates
4 mo
he also said he finds me attractive but didn't want to start anything with me until recently. he also said he likes my personality and that ours mesh well together. calls me adorable and sweetheart.
He says he wants to keep it casual, so why is he acting like a boyfriend?
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