Yes I definitely believe he sexually exploited you! And yes that is considered abuse.

I don't know that you can take the responsibility for what he did to you. You did ask him to stop. Even if you hadn't asked him to stop, your emotional need for a protector and caretaker was so great you clung to that. You were helpless against his exploitations. He could've just been there for you as a big brother, yet he chose to exploit you. So that makes him responsible for what happened.

I better stop right here cuz there's a well of anger rising in me against that male cousin of yours.

Not only was there sexual abuse on the internet but he did it in person as well, when he came over to your house.

It is so confusing, cuz you need his love yet he is using you. The confusion may make it hard to allow yourself to be angry at what he did. I think part of the confusion is that there is both pleasure in it yet a boundary violation at the same time. Kind of like there's a boundary violation yet it is mixed with pleasure of some sort. The pleasure can be physical, or the emotional pleasure of having his attention.

Gentle hugs to you. From cyber-space.