I am so sorry you are going through this!
But think about your self care. Obviously your emotional needs take the front burner right now. Don't try to be actively losing. That's just piling on more stress. But DO try to eat nutritiously so you have energy to deal with all this. DO try to get some sleep. DO try to take care of you. For the most obvious of reasons -- YOU need you to. And your CHILD needs you to.
Taking a time out for just a short month or two isn't going to stop the world. But it will do YOUR self care a world of good to just hit the pause button on as many things as your can so you can focus on your basics. Good nutrition, good sleep, good quality time with kid -- as you figure out your new normal and get ready to tackle the divorce process.
Hitting the pause button on weight loss or dating isn't giving up hope or anything like that. It's taking new information on board, not spreading yourself too thin, and PACING YOURSELF so in the end you can be healthier and happier.
Hang in there!
hugs
A.