It was abuse.
Wait, let me clarify. It was absolutely abuse.
The National Institutes Of Health define sexual abuse or assault as any unwanted sexual advance made by one person to another without consent. Your uncle touched you and you didn't want him to; that's sexual assault. You didn't say if you were a child or not when this happened, but it doesn't really matter. Sexual assault is sexual assault.
You should know that if your uncle did this to you, it's very likely that he's done things like this to others in your family. If you have cousins or other younger family members, I bet they would share similar stories about this man. Incidents like yours are rarely isolated.
You didn't ask me whether or not you should tell your family, so I will leave that to you. But here's my unsolicited advice: I think you should. Abuse like this can continue for years in families, typically because victims are hesitant to speak up out of shame or guilt or fear of repercussions. Not speaking up means that this man's behavior will continue.
Even if not, even if it was an isolated incident, you're still dragging it around with you years later like a sack of rocks, and it would help your psyche tremendously to get it out in the open and deal with it. I'm no shrink, but I do know that unresolved sexual abuse can undermine your relationships with men for years to come. As you see, it's already causing questions in your current relationship.
How you resolve it is your business, but the first step is to expose the abuse to the light of day. You could tell a family member or even a therapist, but I'm not sure your boyfriend is the best place to start. This is an intensely private family matter and not the kind of thing you just want to blurt out to a boyfriend, especially if you are unsure. (My answer to a similar question a few months ago might help you.)
I could be wrong, though -- there's a first time for everything. I'm hoping that any other readers who have been in this situation can offer more insight about how they dealt with it.