It depends what you mean by "prolapsed". Towards the end of pregnancy everything starts to "relax" down there, which means it increasingly loses resistant tone - it will feel the same to DH, and look pretty much the same most of the time, but sitting straining on the loo for 30 minutes will allow it all to drop down a little bit - the result of this is that one can see more of the ridged walls at the entrance, and it all looks a bit more "bulgy". In the last few weeks of pregnancy it will relax even more and look like this a lot.

This is totally normal. So long as you're not in pain, don't have a dragging sensation when you've been on your feet a while, and are not incontinent, all is well.

However, straining on the loo for 30 mins isn't too good because it can encourage piles, while many of us end up with anyway at the end of pregnancy from the weight of bubs. So maybe you want to try, in addition to your fibre, exercise, etc., trying for 5 minutes and if you can't go, go for a wee walk, potter about, and try again...? Or possibly hold off until "i think i need to go" becomes "i REALLY need to go"?

One major plus of all this is that you might well have already discovered somewhere you'll feel comfy labouring - on the toilet!

HTH

Bec

ETA - by all means if you are worried talk to your midwife/Ob - that's what they're for