Need advise please!

I just found out I'm pregnant two days ago, my husband and I split up three months ago i don't know how we started a routine of having sex maybe because we care for each other. We have had many constant problems through these 10 years, I have three kids already so this one will be baby #4 I'm happy but I'm really worried (my kids ages are 14,10 and 8. I don't want to tell my "husband" I'm pregnant because he will want to come back to the house. What I'm afraid of is to go back to being with him with all issues we had in the past, I'm sure he will not change to the man I want him to be. Should I tell him I'm pregnant but prefer to have a distant relationship for the moment or it's too stupid? Or should I wait until he notices and tell him I want to have my baby on my own. I don't want to go back with him. There was no violence or anything like that maybe it was all routine and lack of affection before when we were together we forgot about each other. I want my husband to be caring and lovely like he is now, he is probably doing it because he wants us back but later on he will change to what we were before.