Adult child drama

My son didn’t contact me for 2 years. I wondered what had happened. Recently he contacted me again and was apparently afraid to talk to me because he’s come out as a trans woman and is taking hormones. I said that didn’t matter to me and I was just glad to be talking again. I have no issue with the circumstance of being a trans woman, but what I’m having issue with is that now I’m getting messaged a lot. And I’ve been answering each one and we’ve been chatting regularly. This week it’s been every night and now it’s into days. I really don’t want to be on the phone chatting this much, especially at night. There’s a time difference and I’m getting to bed late. I appreciate that I’m being asked for support so much but it’s getting to be too much. I’m struggling with the thought that if I’m not supportive enough or ignore the messages, I’m going to get shut out again for another 2 years. I’m infringing on my own life and goals to be a “supportive mom” and a “good parent” I have some guilt because I had him young and didn’t raise him directly and feel I have to be there now. Especially during his transition journey because his father, my ex, is against it and it’s a sensitive time. But I have younger children and myself to take care of and a book to write, and I can’t be on call all the time without consequences. How do I handle this?