I think you're probably right. It might not be pain, but just an uncomfortable feeling. Sometimes women don't talk about what makes them feel good because they don't think it's important.
If it IS true that she's feeling uncomfortable, try some different positions. Woman-on-top would be great, since she would be controlling how much of you she takes in at a time.
Just talk it out during a non-sexual time. You guys sound like a great match, so it shouldn't be too hard lol
Oh wait that last line looks almost like a bad joke lol
