My best advice is to just let it happen, as likely, you're going to say it when you least expect it. When my boyfriend said it to me for the first time, it caught me totally off guard, but I felt the same way. It was over the smallest thing– literally me offering him a box of samoas girlscout cookies, and I think of that moment incredibly fondly. It can be scary being that vulnerable with another person, but I'm with nona here
>>112826, there's no wrong way to say it, and no matter what, it's going to be meaningful– it's you expressing your love for him, what could be more special than that?