My 9 yo son has suddenly become possessive

[Paddydaddy]

My wife and I split about 6 years ago and I have my son alternate weekends. Over the last couple of months he has become increasingly upset when I’m taking him home not wanting me to leave to the point of hysteria.
He has also started resenting times that my girlfriend of 3 years spends with us even though until now he has loved her doing things with us. He is cheeky to and dismissive of her.
Is this just his age or should I be looking for something more? As far as I’m aware there are no issues at home

My ds is the same age and he goes through phases when he's completely unconcerned whether he sees his dad and when he is obsessive about it. There doesn't seem to be a trigger. He goes through phases of wanting more or less male company generally.

Does your ex have a new boyfriend? Maybe your ds sees someone potentially taking your place at home & worries that means he will see you less. It might also explain his attempts to drive your dp away. Might be worth asking.

You see him 2 days out of 14? Perhaps make time just for him. How often is girlfriend included in these days? Or does she live with you?