Telling my 3 kiddos I'm pregnant.. why am I so scared??

So I posted earlier about being scared about #4 and now I'm seeking advice on telling my older loves (8,6, 3 1/2). So this is #4 but my first (and probably only) with my boyfriend. My boyfriend is amazing, very supportive and excited but we've only been together 8 months. Now I realize that sounds awful but we went to school together many years ago. Either way it is a lot of change for my older ones as he just moved in with us (he is very stable and owns his condo which he's thinking of selling so we can buy a bigger house as we currently live in my 4 bedroom house)I don't want them in any way to feel loved less because this baby isn't with their dad. Uggghhh any advice is welcome ❤