• having sex you don't really want to
• having sex in any way where you feel like you have to (there was an opportunity, someone else wanted to and expected it of you, etc.)
• having sex because someone else asks for it
• having sex you yourself don't really want or aren't into
...then I think that NOT doing any of that -- not just for a little bit, but not doing that ever -- is the very best choice. None of those things tend to result in ongoing satisfying sexual lives and sexual relationships for people. None of those things tend to result in sex that everyone involved enjoys very much, especially over time. None of those things is actually emotionally healthy.
So, not only is a break a good idea, I'd suggest you start talking to your boyfriend about all this, doing what you two need to through communication and agreements to change it, and then *only* having sex -- any kind of sex -- again when you DO really want to, and because YOU want to, not just because someone else does or you feel otherwise obligated.
If someone won't stay with you if a) you don't have sex with them when they want you to (or period), or b) when you want sex but not in such crummy conditions, then by all means, I think letting them go is the way to go. In that situation, at best you're dealign with people who want different things, but at worst, you're dealing with someone who is just a selfish jerk, and no one should stay or keep having sex with one of those.