I was always taught that when I say no, my partner has to respect that. 100%. No excuses. So, his attempt to manipulate you into sending a picture after you'd already said no and that you were not feeling well is really off. To me, it says, "If I won't respect this one thing, what else am I going to try to get away with"
I know that's probably taking it too far, but it's one of my triggers.