I've been sexually assaulted; and it was only after discussions on here I actually realised it. It was over 30 years ago.
As other posters say rape is penetration of mouth, vagina or anus, so a woman can't do that.
I was woken, stimulated. I was tired & sore. I said no, I didn't want to and tried to push my GF away, she was insistent and in the end I stopped struggling with her. She produced an orgasm from - and for - me, and I rolled away from her.
I told her in the morning never to do that again. I kept going out with her for a year, because I was so in love with her. But she assaulted me; I didn't want to, it wasn't comfortable and it felt sort of sleazy.
So, not fighting, and even orgasm is no evidence of consent. Saying no is very clear evidence of no consent. Previous consensual activity isn't consent for more activity. Not saying no, doesn't mean consent either.
I often wondered how women could see someone again who'd done that to them. FWIW, it wasn't an "Oh, that was great, I'd love to have that done again" type of experience. It was unpleasant, and made me think less of the woman. She? She thought I'd enjoy it... I didn't.
I didn't think about it too much at the time; looking back on it, even in the context of an otherwise loving relationship it was wrong. I can see why some women can be conflicted.