I need a little bit of advice

[PrinPeach]

I'm a first time step mum (25) to a lovely little 3 year old boy. Me and my partner have recently started having him every other weekend as my partners working hours have now changed to thankfully allow this. The first few weekends ran smoothly but recently he has started asking for mummy and crying on and off all day. I obviously understand that it is completely normal for his age range and that all babies just want their mummy. I'm seeking advice on the best way to soothe him. I currently tell him that mummy will be coming to collect him Sunday morning and that he can look forward to seeing her soon. This works but then after 20 mins or so he will be asking where mummy is again and crying. How can I help him navigate his emotions? Any advice is welcome :)

Don't take it to heart op.
There's a contingent of people who aren't step parents who only post on this forum to bring step parents down. They are pretty easy to spot so just ignore them.

Don't know if anyone above suggested stuff like bringing a familar toy from home. It may be that if there are things he does at the weekend at Mum's, it might be useful to do some of those - watch a particular programme, go to the usual park/soft play place (if there are not large distances involved), make some familiar/favourite food. Perhaps establishing a kind of being-at-Dad's-routine, will help.