If there is no itching or burning sensation at other times-I'd say it is normal cervical mucous.
It may be thrush-but without the soreness, it's hard to say.
It may be due to lots of thrusting while being well lubricated as w ell, kind of like foam-or soap suds.
Is it similar to whipped egg whites?-then this is probably what it is.
If you don't notice your own mucous texture during the rest of your cycle, (you may occasionaly see-sticky white discharge-this represents an infertile time)
Read this:
Cervix - Wikipedia, the free encyclopedia