Welcome to TeenHelp! I hope we can help you with this.
I think what would be beneficial here is setting some very clear boundaries. I get why it's tempting to either completely give in to his affection or distance yourself by miles, but if you're willing there is a middle ground. You could have a conversation with him about the nature of the interactions you're having.
Beforehand, I would think about what it is you want to get out of your relationship with him. Write it down, if you must. If you feel super torn about it, you could always turn it into a pros and cons list, and that might help. Once you have your list, you can prepare what it is you want to say to him.
When you do speak with him, it's important to highlight a couple of things: no, you do not want to be physical anymore, but yes, you value you his friendship and want him in your life- as a friend. Now he may have some difficult feelings about this, but those are NOT your responsibility. Your responsibility is to set healthy boundaries for yourself. You deserve to feel good about your relationships, and boundaries are a part of that.
As for not being used? Sadly, there's no real answer for that. You could wear a burlap sack and men will still objectify you. That's just the messed up society we live in. However, you don't have to put up with it. You can speak out, if you feel safe doing so. "No" and "Leave me alone" are complete sentences. You don't have to justify yourself to anyone.
I hope this helped.
PM me if you need anything.