he has a soft toy that he's had since birth, which he loves to bits. he does this thing with it though, where he lies on top of it and, basically, for want of a better description, humps it. He has done it always, i remember him doing it when he was less than a year old... he generally does when he's tired... but now that he's a bit older it's sort of embarrasing if there are other people around, as it really does look like he's trying to have his way with it, and his breathing becomes very quick and shallow too, which doesn't help.
i've asked him what he's doing and he says 'i'm wiggling my teddy'. i don't want to make a big deal out of it, but i don't want him doing it in public / at nursery, because people will think it odd.
is this common? am i worrying about nothing?