Visiting family

My mum and sister live 2 hours from me since I moved out 3 years ago. In that time they’ve visited me twice between them, I’m always the one visiting them and they expect me to visit at least twice a month.

I don’t mind visiting them obviously but I’ve been so busy recently, working and have college, I barely have time for myself and it costs money travelling. It upsets me that they never take the time to come to me but they always make excuses. My sister is never busy and my mum works a lot less hours than me. I haven’t been to see them since Christmas and won’t going back for at least 2 weeks and they’re making me feel bad. I’m sick of it but they still make me feel shitty when I bring it up with them. Does anyone else ever get this problem?