Repetition is not necessary for an act to be abuse, nor is removal of clothing. Oral penetration may or may not be specifically quantified as rape under the laws of your state, but can certainly be abuse.
Victims may "go along with" abuse in order to protect themselves from further harm, or to protect other family members or others that they care about from harm.
I hope that information helps. I am very sorry if something bad has happened to you. Please don't be afraid to seek help if you are struggling.