Happy81 I have a DS age 2.8 who is just the same. It's been going on for a while now, he used to like going to playground, shopping & cafe, farm etc on my days with him or on weekends but now definitely prefers to stay at home and play with his toys.
I'm not entirely sure what it's all about - it's difficult because he goes to a childminder 4 days a week while DH & I work. So I don't know if in his mind he's already 'gone out' when going there and just wants to chill with his own toys at home.
He has also gone through a bit a change, starting with me going abroad for work for a week, he was quite disrupted when I came back, then we've done potty training, moving to a new room and switching to a big bed all in the last 4 months.
I think he does enjoy going out still, he just knows that there is often a choice about what we do together on my day off or weekends, and so he makes his feelings known that he'd rather stay at home.
Oh, this might also just be part of his personality...his Dad is just the same, would much rather stay at home than go out. I need more variety than that. I also get the dreaded 'should' guilt - as in, I SHOULD be spending our time doing fascinating and educational activities. I've learnt that any thought of mine that starts with 'I should' needs to be questioned though...there are a lot of 'shoulds' that aren't that important really. Obviously if I need to go out to get something or for my sanity, then that's a different question.
Anyway, I just wanted to let you know that you're not alone with a homebody child.