Helloooooo, I have had this problem on and off since the birth of my second giant DC 3 years ago.
Since he was born I had the heavy feeling, iykwim, I saw my gp who thought it was a prolapse although not actually out (internal - pelvic wall collapse or something similar). I went to the Gynae Consultant when DS was FOUR WEEKS OLD and he charmingly informed me it would help if I LOST SOME WEIGHT!!! How I didn't lamp him I don't know.
Anyway after lots of pelvic floor exercises it did get a lot better. Constipation contributes to the problem as any (TMI) pushing causes it to be nearly pushing out.
My ongoing problem is exercise makes it worse. I'm a normal weight so weight isn't the issue but wanting to lose a few pounds and definitely tone up I took up running but had to give up after a couple of months as it gave me the heavy feeling and felt like something was pushing out. I started the gym doing general exercise classes and again got the heavy feeling as though something was pushing out. When this happens i think that if I continued exercising then it will actually come out, I just stop in time when the feeling starts.
I am going to start to do yoga and pilates which is supposed to be good for this. Also the pelvic floor exercises helped me. I was referred to a pelvic physiotherapist nurse who was fantastic for me advice wise and also mindset.
Can I please say OP that all of the GP's, nurses etc that I saw were amazingly supportive and helpful (other than the Consultant I saw). My GP said that intercourse is absolutely fine in circumstances like this and if anything, it actually pushes it back in (!!!!).
Sorry for such a long post but it is an ongoing part of my life and nobody talks about it, you cant' get info from the internet and it's kind of unspoken. I was thinking of starting a thread of my own yesterday so i'm pleased to see some people to share conversation with about this!