OP, really sorry you are in this position.
My Dad returned to my Mum, but they were older, he had had a mid life crisis and did the cliched thing - affair with younger woman. He was gone about 8 months. Then discovered that OW did not look after him as well as my Mum, not emotionally, domestically, weren't such good freinds, etc.
I would guess it depends on why he has left. If you basically had a good relationship but he has panciked / had a mid life crisis about having 3 kids, whether your relationship had been failing and you both knew that, whether he has been deceiving you about being happy and took a chance when he saw one...what reasons did he give?
Some men use one woman as the catalyst to leave a marriage and then leave that woman but don't look back.
In your position I think that you need to be taking as much care of yourself as you can and building towards a solution that does not have him at it's heart. Then you have more confidence and if, IF he comes back, you will be all the stronger and clearer, and more equal in your relationship, for knowing that you could have bloody well managed without him. If he has gone out of panic, seeing you needy will be the last thing to bring him home.
Find your own strength. Good luck.