inspired, your post shows me a couple of red flags right off the bat.
You're together seven months, you're sexually active, and he doesn't know about your fetishes? To me.. that would seem a pretty long time to withhold a fetish from a partner who you are intimate with. It seems to me that up until now.. you either felt him and the relationship more important than the fetish.. or.. you just don't trust him enough to tell him.
Telling him could cause one of a few things to happen. He might be willing to accomodate you.. to make you happy, and you might be able to get some tickling in. He might say. "I can't deal with being tickled.. so you either have to accept that I dont like to be tickled.. or.. we may have to break up".. He also might be angry that you withheld it from him for that length of time.. and he might feel that you either dont trust him, and that he cant trust you.
I havent been in a relationship in a while.. but.. for myself., as I have both a foot and tickle fetish... I would handle it this way. After being intimate for however long.. I would say to the girl : "Can I massage your feet?": If she balked, and said no, I would probably have to then spill the beans about my foot fetish, and then tickling, and see what her reaction was. If she said. "You can never, ever touch my feet", that, would probably turn me off, because my reply would be: "Why can I touch your breasts, sexual areas, etc, but not your feet". As for tickling: If I said to the girl: "I enjoy tickling.. do you mind if I tickle you from time to time". Again, I'd have to see the reaction. Such would also highly depend on what else I had in common with her, how I felt about her, and how she felt about me.
The real question is going to be which is more important to you. Your boyfriend.. or tickling. You may well have to choose. I think its harder for a ler to tickle someone else who doesnt like it.. because.. the reality is.. many vanillas dont like to be tickled. It is sometimes easier for a lee to say to their partner... "Please tickle me", because the partner isnt the one who is enduring the tickling, and physical reaction that goes along with it.
Either way, I think you have to tell him. Hopefully, he will be understanding, and accomodate you with allowing you to tickle him, at least from time to time. If he completely balks at being tickled at all, then, I hate to say, you then have a difficult decision to make of which is more important.. tickling.. or him. If he is.. then you might have to live without tickling. If the tickling is more important.. you then need to part from him, find someone who is okay with being tickled, and bring up the tickling earlier in the relationship.
Situations like this are very difficult. I feel for you, because I know this might well happen to me at some point, with finding a vanilla girl who wouldnt like to be tickled. If I were you, I would have a discussion with him about the situation, and I hope he is open minded, and receptive enough to be open to letting you tickle him at least sometimes. Good Luck.
Mitch