My wife and I had tried anal sex and it took some time to get past her anal muscles. A couple of weeks later we were having vaginal sex when I slipped out of her vagina and into her anus but accident, unknowingly to me she said "that's my butt". Surprised on how easily my penis penetrated her anal muscles, I became worried that she may have had anal sex earlier that day or day before. So how easily is it for a man to penetrate a womans anus with her being new to anal sex?