I have frequent wet dreams?

I am 18 years old. I first started having wet dreams when I was about 12-13 years old. I would have about one or two a month. That continued on until I was 16. Then they stopped. Just a few months ago I started having wet dreams again. I didn't pay it any attention at first, but now I am having them nightly if not more. One night last week I had three. I tried upping the amount I masturbate and masturbating before I go to sleep, but that has failed. What is happening and what should I do about it?