Clueless communication

So I am currently with my amazing boyfriend and I love him, but lately we haven’t had much time to spend together. He has a young child from a previous relationship so it is difficult for alone time. Recently he has been making plans to spend time with me and it ends up he stays out too late with his bros or something comes up. I am terrible with communication so instead of talking about my feelings I’ll just make sarcastic comments so he understands I’m upset. I need advice on how to productively share my feelings instead of letting my anxiety cause tension between us. Please help. I want this to last, but if I keep this up I know it won’t.