Sometimes, the best way forward is just to say it. Don't worry about communicating it
well, just start the conversation. If it helps, write down a few things and practice saying them before you see him. Play out a conversation in your mind.
Example:
"I like having my feet tickled."
"Why?"
"I like the feeling of losing control. I like the feeling of surrendering to you. I enjoy the sensations of being tickled."
"Is there anything you want me to do?"
"Yes. Attack me randomly when we're together. Plan out a tickling session for us."
Most of us have been through what you're going through. The hardest part is usually just taking that first step. But the more you talk about it, the easier it will get. Trust me.