sexting for the first time

my boyfriend sent me a text last night saying how horny he was. I felt bad cuz we haven't seen each other in some days and won't be able to see him until next week (college). anyway, I decided to get out from my comfort zone and I started sexting him. last thing I sent was a picture of me moaning and he only said: "Nooooo I love what you're doing but I can't handle it right now" so idk if he didn't like it and hated it. I have not sext before so idk if what I did was wrong. are there any good tips for sexting?