Do I have the right to be upset?

Hi everyone.. So my bf is away for 4 months for the summer. For the first month we're talking everyday and things are just as lovely and stable. Lately, he started answering me days later and he stopped calling me. I didn't say anything because I'm thinking he must be busy and having fun and all I want is for him to be happy. Recently, he's been reading my messages and not answering them. Just leaves them on read. I just told him that he's been ignoring me and he told me to 'Chill! Chill!' I should also mention that he recently (within the last week) made all his social media accounts public and has been promoting his snapchat after making it private when we got together. I can't help but feel like I dont mean much to him anymore and its really affecting me. I don't know what to do. We've only got together since late March and I haven't seen him since May.