I’m confused & sad 😣

So I’ve been having sex with a guy for last 3 months and he said all his friends & sister know that we’re together. he never ask me to be his gf or talk about relationship but I think he sees me as his gf not 100% sure though. and I don’t mind being his gf. What I’m sad about is that He never really make time to see me, like I know his working and studying but he has days off and if I try to see him on his day off he says his sister will be pissed. And he loves his sister they’re very close and live together. He says his sister will be lonely if he leaves the house to see me… like wtf? The only time I see him is when he has absolutely nothing to do and his sister is at work and can’t hangout with her. am I being jealous of this sister? I’m I the problem I have never met any guy who’s obsessed with his sister like this. Maybe I’m overthinking I need advice on what I should do…. 😭