What Can Cause Heavy Flow Of White Discharge ?

I'm 25 years old and it's been a week since I've been itching down there and seems like a have a lot of pasty white stuff coming out more than normal but on the other hand I had sex with my husband and as soon as he penetrated it began to swell up and burn I have never been experienced anything like it, so my question is what is causing it to itch and swell up? Is this something i can prevent from happening again or do is it serious?