I need advice from working mommies?

Take one day at a time and one hour at a time. Thinking about it is often more overwhelming than the actual event, and while the first days of separation are going to be difficult, remember that children adapt to new situations, and this situation, although different to what you had going on before, is not a bad one. He is in safe place with people who care about him and you. The fear of something happening to our kids never fully goes away, but if you have chosen people you fully trust, it isn't going to be a problem in the future.

Talk calmly and casually with your mother and your so's father about how they plan to spend their time with the baby, to give you some peace of mind and security. Uncertainty makes things more difficult but if you can have an idea of what your son is doing (most likely sleeping considering your shifts) at a certain time, the anxiety is more manageable. To help your son to make a smooth transition, visit your mother and so's father often, and if possible let him nap and eat in the places he will be using at their homes. He will get more familiar with the surroundings and its best if you can do it at a gradual phase.

The first weeks are always the most difficult and demanding, but there is a light at the end of the tunnel, I promise you.

A lot of the way you are feeling is due to hormones. Try to keep that in mind so you can put aside the hormonal thoughts and think rationally. You are doing what is best for both you and your baby, you are continuing your life and being a role model, you are providing for him, you are leaving him in excellent care. You can't logically spend 24/7 with him for the rest of his life. He will be fine, and you will be fine, and you will both adjust after the first few days which will be the hardest. Just don't give up and be strong.