HEH, this sounds exactly like Harvey. Except he does it with my cats, not me any more. Since I gave him meds for a good couple of weeks, he has stopped circling me. With the cats it started as circling, then add in peeing on them, to finally humping with a random foot thump thrown in. He mostly just does it to Merlin. First thing he does in the morning when I let him out, hump Merlin.
He isn't fixed yet and I'm reallllly hoping it helps haha.