Happy when he is here, sad and resentful when he is not

I love a person who works almost all day, has kids and wife, he doesn’t live in the same city as I do, in fact he lives far away, we chat everyday (not all day) and do video calls almost everyday.

I am happy when he contacts me and when he doesn’t I feel sad.

I feel sad and resentful, because I feel he contacts me whenever he wants and has the opportunity and I’m always there for him, but when I want to contact him, I text him but he doesn’t reply until he wants or is available… so my question is how can I feel good with him calling me or not calling me? I don’t want to feel like a wind vane anymore, thank you.