Not really sure how I feel about this

So I've been talking to and hanging out with this guy for a few months now and I thought everything was going fine...like he called me beautiful everyday complimented me on my eyes,hair,face, etc. We walked together at school (I'm in high school) we went out on dates and even hung out at each others houses multiple times.And then Sunday morning I wake up scroll through my feed on Instagram and there he is with a prom poster with another girl. He asked another girl to prom while we we're talking to one another. Then he has the nerve to snap me "hey beautiful" like he didn't just ask another girl out..publicly....I haven't said anything about it to him but there's no way he doesn't know that I know...idk just feeling kinda stupid cause my gut told me to go for him but all my friends said not to and I didn't listen....