Help my son has baby fever

My 9 yr old son has baby fever for several montha now and I think it is worse than my boyfriend and I. He walks around talking to my belly and already named the new baby... which just to clarify we are ttc#2 and it has only been about a on the that we have trying..... I have told my son that I'm not pregnant and he still continue on....... it got to the point where he told his 3rd grade class and the teacher said congratulations. I was embarrassed. I told the teacher that I wasn't and she said well your son has been telling the whole class for couple weeks about his baby brother Michaelangelo...... so needless to say I explained to the class that there is no baby yet it was an April fools joke early......it was slightly embarrassing..... any advice on how to tame down his baby fever??? He has two cats as pets that he calls his babies but he still thinks I'm pregnant... I need help please