Ready or Not?

Between the hubby working 6 days on, 2 days off, having his ex to deal with for his 5 year old son's sake (as we primarily raise him, yet the court has her as the "residential parent" for school and child support reasons), and also having our daughter turning 2 soon... Yes, I would like to return to school soon for myself (college), but... Me being 24 and husband is nearing 27, we know we're still young to wait for another, but... I'd also like to get my life into drive soon... I guess I know it's purely up to ourselves, but I just don't know if having one more baby NOW would benefit us, as a new baby could arrive as I'm going to school, or waiting until AFTER my bachelore's degree is done? (Already have my Associate's)...  As of now, I'm a stay-at-home-mom for both of our kids. It's amazing how flexible my lifestyle is, and I'm very thankful I get to live it. But the husband and I have discussed many times we'd potentially like another baby, then it would be our last child as well. My siblings, growing up, when I graduated, I was 18, my sister was 11, and my little brother was born a month LATER! I couldn't go to the park with my little brother without someone being confused asking if he was mine!?! Lol.
 I don't want to do that to my children... Though there's nothing wrong with it!! :) I guess I just know I want one more and trying to decide if NOW is right or if maybe even accepting the 2 children in my life I have now should be all I want? I feel selfish in a way, asking for opinions, but I'm really not. I'm only asking for guidance. I'd appreciate no negative comments as well. Thank you.