I'm confused as to what to do...

I need help. I keep getting mixed answers and I just need some input from some mommas. I am 10 weeks pregnant and the baby's father walked away. The day he did, an old flame of mine told me that his for me haven't went away. We never got a real chance to try because he was stationed in Japan for 4 years. I wanna try, and he knows everything and wants to be there for the child, but I also need to think about my child. I dont want someone to enter my life and decide that they've changed their mind. I do care about him and want to give him a chance, but my baby comes first and dont want him/her to get used to him and have him walk away because they aren't his. Any advice?