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. Putting your body weight on a partner evenly is important, as is spreading the weight over a broad surface area. Elbowing someone in the ribs, we all know, puts a lot of force on a very small area and can hurt quite a bit. You can use your palm to press on another person's body with the same amount of force, on the other hand, and not hurt them at all. The same principle applies when you straddle a partner's head or hips.