In my opinion it's worth a few seconds of not getting a good breath to give a lover a great orgasm, but your mileage may vary. Crushing is even less likely than suffocation or smothering. The human body is a pretty sturdy thing, and when someone lies on top of you or straddles you, the weight generally gets distributed pretty comfortably, especially if the person on the bottom relaxes and lets their body adjust to it. Many people find the sensation quite reassuring, if not downright erotic. It just ain't so.
Communication is key.
It can be a little scary to let a lover take your body weight, no matter how much or how little you weigh, but if your lover is enjoying it and says so, it's okay to go ahead and do it. Sometimes, muscle tension or other factors may make that kind of pressure uncomfortable even for people who normally enjoy it. If it's not working, don't worry about it. Tomorrow is another day. Switch positions and try something else.