Knott knows what she's talking about. If you can relieve the pressure by sitting up, that's a huge red flag that it's your posture that's the problem. Try sitting up to where it doesn't bother you, then leave your pelvis where it is when you come back down to the bars.

But another thought ... indoor bikes often come with really bizarre saddles that don't fit any known human being. If the saddle you were sitting on didn't allow you to put any of your weight where it's supposed to be, it's remotely possible it might've thrown you that far forward.

Do you have the same problem on your outdoor bike(s)? If not, does your gym give you the option of bringing your own saddle? I can't imagine a saddle fitting so poorly it would be contacting your pubic bone *without* giving you excruciating soft tissue chafing first - but we're all different down there.