General Uh oh....

I will let for others to chime in on your other questions, but you should separate the male immediately from the females. I would double check the sex of all the others as well.

Yep, turn 'em all over and compare their private parts and separate into piles (and a different pen) accordingly.

The females may or may not be pregnant. They come into heat every 14-16 days, and a herd of sows will usually all come into heat around the same time if they've been together for a while.

If they are, it will be weeks before you'll know. See https://www.guineapigcages.com/foru...inea-pig-is-pregnant-And-how-far-along-is-she.