I found out just how sensitive my breasts can be when I was dating a man I didn't trust enough to fuck. He was, however, devastatingly handsome, and he was very into me, and I'm enough of an opportunist not to let such a combination go to waste. I wasn't willing to go all the way with him, but we sure did get a lot of mileage out of necking and petting above the waist. There's much more to sex than the line drive toward orgasm. While we've gained, culturally, from losing many of the fears that engendered that state of affairs, I'm not so sure that we haven't, as a culture, lost something from the standpoint of sensuality.
Sex is more than genitals, and necking particularly is an underrated joy.
There's a spot on my neck just below and behind my ear, for instance, that sends rivulets of shivers down my spine whenever someone lets their teeth drag lightly over it. I didn't know I had that spot, or that sensitivity, until I was nearly 30 and dating the untrustworthy but beautiful man I mentioned earlier. There were moments with him when I wished I hadn't already decided not to fuck him. But I'm glad I put up those boundaries in that relationship. While it might sound a little like a BDSM credo when taken out of context, I think this has relevance to your situation.