Now I'm getting upset... what should I do?

Long story short, I've known my crush for about 10 months now. He flirts w/ me, talks to me, just an overall awesome guy. But one problem, he flirts w/ another girl in front of me. I get that he's single and he's allowed to do that...but it kinda hurts my feelings and pushes me away. He flirts w/ my 'sorta' friend, but as he does it he'll give quick glances at me. Before I could never tell, but lately he's been making it really clear. It's pissing me off and tbh, I'm thinking of trying to end this 'whole' crush thing. He's a little younger than me so he's quite immature. He talks to many people especially girls in the most confident way....but as soon as he gets to me, he's mellow and sorta shy. That's only sometimes and he knows I'm shy as well. . He doesn't know I like him and I don't know what to do. Any suggestions??
Now I'm getting upset... what should I do?
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