I agree with the others on getting another female or two to help with the "randy" male. However, in my experience, sometimes this does not help. I have had a few male Platys that would only pay attention to ONE female, no matter how many there were in the tank. They seem to be more monogomous then some of the others.
I had a Blue Platy male that was in with 4 females, 2 White Mickeys, a Red Wag and an Orange High-fin. He did not like the orange ones at all, but, he didn't like ANY orange fish. It was really funny.......when I dropped in Algea Wafers, he would "guard" one and keep all the orange fish (Swordtail & Platy) away, but let the Green Swords and White Mickeys eat from it with him. He was seriously color biased.
) BAD FISH!! Even worse, although he allowed both Mickeys around, he only bred with one of them, and payed no interest in the other.
Just info I though you might like.