I hate to be the bearer of bad news, but it sounds like you are having a prolapse of some kind (mine was a vaginal vault prolapse).
I strongly urge you with the most emphatic voice possible to get thee to a urogynecologist ASAP
. Most ObGyns will not know how to deal with this in the most effective way, nor will a urologist. Urogyns have gobs and gobs of training specifically about how to deal with these issues comprehensively (and trust me, it makes a difference!!!!)
You can find a urogyn by searching at http://www.mypelvichealth.org
. That website also has a lot of good information as well so be sure to check it out.
There isn't much that can be done until after baby comes, but your provider needs to be aware of it because prolonged, extended, and "purple pushing" can make this far worse than it is right now.
Just as an aside, research has shown that women who suffer from SPD/DSP in pregnancy are much more likely to develop prolapse issues either in pregnancy or later in life. The SPD is an early indicator of laxity in tendons and other supportive fibers. Sometimes
Kegels can help, but depending on the cause of the prolapse and where it is located, they may not help at all. This was the situation in my case - my prolapse was caused by precipitous labor and tears to the supportive fascia underlying the vaginal muscle. I could have Kegel-ed until I was blue in the face and it wouldn't have "fixed" what was ailing me, which sounds exactly like what you are dealing with.
Best of luck - I do know that the earlier you seek treatment, the less problematic prolapse are and the more easily they are treated!