I'm so sorry about what your grandfather did to you. A child cannot consent to sexual activity of any kind. What your grandfather did was an invasion and taking advantage of a child's trust in him.
You were indeed conditioned to say yes. He groomed you and manipulated you. By the time you begin to question what he's doing, it's only natural that this would confuse you.
"If I had said no he would have stopped." A lot of times, someone sexually abusing a child does not respond to "no", and sometimes the child knows that saying yes might make things go faster/get it over with/ and not anger their abuser, especially since the child may fear angering them with their "no".
I'm glad to hear online resources have been helpful for you (I'v used RAINN online twice and found them very supportive!)
I would encourage seeking out therapy, because this seems to have a (completely understandable) effect on your current life. Sometimes the emotions need help coming to the surface in a safe space, and to be witnessed by a safe person. Sometimes we desperately want to get in touch with those emotions, but our mind has created a disconnect and/or tries to protect us from feeling overwhelmed with the emotion, if that makes sense.
Depending on your age and whether or not you're still in danger, your family would not have to know unless you chose to disclose to them.
Is there anyone in your life - friend, pastor, general practitioner, etc. who you would feel comfortable talking to? Is seeing a therapist something you'd be interested in?