Some good advice from Starry here.
I'd also recommend that you simply take a break from intercourse, too. For say: 2 weeks. Do everything but intercourse. You might discover some new things or discover sensations you had completely forgotten about.
And really, if you aren't comfortable doing something like masturbating in front of your partner, then don't do it. I think your partner should better not pressure you into things you do not want and rather accept your boundaries, because if someone doesn't do that, he just isn't a good partner to have.
Hope this helps a little, gal.
~spanking new Scarleteen Sexpert~
"We must become the change we want to see."