Yes, I give her oral sex and she really likes it. I guess I should be more thankful.
Yes ask her to do it more, if she doesn't want to then so be it. Maybe she doesn't really like it and said that it is ok for your benefit. Maybe she is doing it to make you happy and once a week is all she wants to do it.
Also iam1butterfly is right you should be asking her what she likes and wants. Do you give her oral sex?
No, it's not wrong to ask.
Otherwise, how could she know that you like or want more *******s unless you tell her? And, while you're mentioning it; why not ask her what she likes?