Stuck with our next step

[ninjashark]

DD is 26 months and has been potty training for just over a week, it's went really well and we're having no accidents at all when she's naked from the waist down, I'm not even having to prompt her anymore she'll just tell me "I need a wee" and go sit on her potty.
The issue I'm having is as soon as she has pants on she treats them like a nappy and will just wee/poo in them.
I've tried going up a size so they are loose and leaving pants off and just putting trousers on but neither seem to work. I've also gone back to sitting her on the potty every 10-20 mins but it doesn't matter how long she's sat there for as soon as the pants are back on she'll go.
Obviously in the house she can stay naked that's fine but I wanted to try and start short journeys/outings soon and I've no idea how to get her past this. Help!

Going straight from naked to trousers and pants can be a bit much. My DS was in joggers with no pants for quite a few weeks. I was nervous about introducing the pants because he was doing so well without them but actually it was fine once we did. But when we went from naked to joggers it was messy again for a few days. There is more learning for them to do at each step of the process and I think you just have to work through it and let them get used to bottoms and accept the accidents that come with it while they get used to that stage. It’s v common for them to be doing super well naked and then have issues again when bottoms are introduced. We did a combo of naked in the house to keep him feeling that he’d made progress and joggers for trips as short as the five minutes round the corner to our co-op initially. Then he just kept the bottoms on more and more. So it can be a gradual process and don’t be disheartened if it feels like you’ve gone backwards when you move onto each new stage. My DS was around the same age as your DD when we did it.