Pregnant mouse question

Well I think my mouse is pregnant, she is getting fatter, my question is, do I need to separate her from her mate if she is? they have been together from beginning and still they house together in the same bedding place, he is very, I mean VERY laid back, I think she may be the alpha if there is such in the mouse community. but when I take her out to hold her he kinda squeaks like he is lonely in the home, I would really hate to separate them, is it dangerous for him? because I seriously doubt he would hurt anything, as I said he is extremely chill.
also what do I need to look for in her through the pregnancy, I read it takes 21 days. is there something I should be feeding her more?
I know that once she gives birth I should separate them so she doesn't get preg again but would rather prolong the separation if I can

Mouse pregnancy is between 18 and 21 days, normally.

I would say definitely separate before she delivers. If you don't separate, she will become pregnant again almost immediately after delivery. Mousie girls do that; they come back into heat very, very soon after they deliver and it's very hard on them to have litter after litter like that back to back. It would also shorten her lifespan.

Bucks do fine on their own. Don't get me wrong, they like company, but there's no easy solution. I recommend getting him a decent sized cage and filling it with plenty of toys. Even cheap things like toilet paper rolls, squares of fleece that you can hang with zip ties to make a hammock, a house for him to hide in... I have a few cheap toy ideas that you can make using toilet paper rolls if you'd be interested. Just PM me.

thanks, I have three cages, they are in two cages linked together by tubing, can I just split up the tubing and keep them side by side but not able to get into each others cages?

That sounds perfect! Be sure to take photos when your little ones are born! I'd love to see them.

ok another question may sound dumb but....
I am afraid to clean the cages, I don't want to stress her, if she is nesting for a place to have the babies will it be ok to clean the cages? the one cage she seems to spend the most time tearing things up and chilling in when she isn't with sonic has food all on the bottom, (I use old clothes for bedding btw), it isn't smelling badly in there should I leave that cage alone? or try to clean up the food and not change the bedding? there is a hide away spot off the tubing that she has fixed with bedding cottons bought from store that I won't touch and I don't touch the old card board salt container where I see them sleeping, but the other cage she has built a bedding area in the whole cage, not in any removable bed. if that makes sense.

I change bedding 2x a week in my cages at home and I usually remove nests and all, even with pinkies. I haven't really noticed any issues with it.

Sometimes if I feel bad, I'll leave the nest portion, or I'll put the nesting material back the way she had it after I clean.

If you can clean around the nest, do that.

It doesn't sound dumb. A lot of animals get stressed when their pregnant. For instance, hedgehogs will kill their entire litter if they're stressed. Pregnant/birthing hedgehogs stress ME out! lol