The counter is the closest thing that is available in relation to their x-pen. With these little buggers it's hard enough working with one without having three more jumping around too!
They're lovely puppies - I love to see them when their noses are just getting colour. I think the tri girl looks very promising - have you a favourite?
Did you confirm pregnancy? You need to get her to a vet. They will probably need to do x-rays and if an ultrasound is available then ultrasound to check heartbeats for fetal distress.