Advice please! Pregnancy after a breakup…

I broke up with my ex in may this year, we hadn’t been close in quite a while, I was very unhappy, he was unwilling to work with me to make things better. We were together 13 years. We have 3 children together ages 5, 3 and 9 months. I moved out temporarily to my mums until I can find suitable housing. I started chatting to an old friend whilst I was going through the separation and we have gotten close, due to a contraception issue I am now pregnant with his child. Me and my children’s dad co-parent very well and I still care about him and I don’t know how to tell him about this news, I don’t want to hurt his feelings.