Will my son be okay if I leave my husband?

Hi, I have a one-year-old son. I’ve been dealing with postpartum depression badly, and I recently caught my husband cheating on me twice in 1 weekend. That was a few weeks ago, and now I’ve discovered the girl he has been cheating on me with was under his brother’s contact on his cell phone. My question is. What should I do? Once I’ve tried to leave him, and my son got sick with diarrhea and would not eat… Will, my son, be ok when I leave for good?