This is my second marriage. No kids from first marriage. I often find myself thinking of my first Husband and wondering if things would have been different if we had children. Maybe we might still be together. Is it ok for me to feel like this?

I do think about my ex bf a lot although I am happily married now. Even my husband would sometimes wonder and asked me how my life would be if I had stayed on with my ex bf then. I think it's normal as humans are curious creatures. As long as this curiosity doesn't have a negative impact on your current marriage and you do not allow yourself to live in the past but take the past as a motivation to make your current marriage an even better one, I think it's fine. Perhaps find a common hobby with your husband and immerse yourself in new things to occupy your mind if these thoughts bothers you.