Our well behaved 3 year old black lab mix has started pooping and peeing in the floor. The first time it was during the night and the next time she pooped a foot away from me while I was doing the dishes. Our schedule has recently changed so we think that may be the problem but how do we proceed? We were advised to get another dog to lessen the separation anxiety but are worried we will then have to dogs pooping in the floor. Help?

Another dog doesn't always solve the problem.
Have you heard about the separation anxiety method of leaving the dog at intervals?
You go out at random times during the day and just leave for a few minutes, then come back.
As time progresses the amount of time you leave for gets longer and longer.
So if you leave for 1 minute the first time, you leave for 2 minutes the next time, then 3, then 4 etc etc
It helps the dog realise that when you leave you are going to come back.
When was his last vet check?
Sometimes there can also be medical problems at play and he may just not be able to help it.

I'd first make sure that she doesn't have any health issues.

Is she used to being let out into a yard to potty or is she walked? Does she wait to be taken/let out or does she have a 'cue' that lets you know she needs to use the bathroom? Has her feeding schedule been changed? She may be adjusting to a new schedule for feeding and going to the bathroom.

You haven't mentioned any problems happening while you are gone so I am not sure separation anxiety is what is wrong with her. Has she had any other behavioral changes?

Sometimes, a playmate can help. However, if she is already having issues with separation anxiety (or just plain anxiety), she could see the newcomer as a potential replacement or rival for affection. That would just add to your problems.