Ok...so ask her, put her on the spot about it. Now...to ask another question (I'm good at asking questions LOL)...could it be HOW you are touching her? Could your touch be too hard/soft?
Speaking from my own experience...my H has a tendancy to be too light-handed when touching me and it tickles. I HATE, absolutely cannot stand to be tickled...it kills that sexual spark dead for me. So ask questions, try different touches...better yet...give her your hand and aska her to show you the pressure she does like.
Have you explained to her that it's not just the physical aspect of foreplay that you are missing?