Breakups

How long on average do you give yourself to get over a break up? I mean, some people just wait until their healed and there's no time limit. But I know some people actually give themselves a few weeks or whatever to heal and put themselves first. What works best? Struggling at the moment but the biggest dread I have is the thought of him with someone new, and loving someone else. That though kills me. This is hard, I feel sick all the time. No appetite. Can't even function properly, every day is just going past in a blur. It's such a horrible feeling, we're still in contact because we have a baby, but he acts as though he's already over us. But in the next breath he still wants to come on the family holiday we have booked for for next month. I dont get it