School and Babies

So I just started school again after 4 years, I am very excited, I only need 7 classes to get my associates degree and then I plan to transfer to another college to get my Bachelors. Not to mention my husband and I have been talking about another baby, we are not sure yet, I have always wanted 3 kids but things with the two are so good right now, I am afraid I will regret the decision to have another baby if it messes things up with the girls, I feel guilty thinking about another baby, I think mostly because I feel like Ellie needs a lot of my time, she is very jealous of her older sister, I am not worried about Eden though, she wants another brother or sister. She said Ellie is her baby and now Ellie needs a baby for herself. Then my sister and grandmother say we shouldn't do it now because of finances and the economy but if everybody waited until they were financially secure then nobody would ever have kids, because there is no such thing as financial security. Babies don't cost a lot anyway, it is when they get into their third and fourth years that they become expensive. Anyway, I am just very nervous, not to mention it is just getting to the point where I can finally get some breathing room from the kids and go and have fun for a while, but that is more scheduling and planning than a real issue if we have a willing sitter, which is hard to find, my family is so unreliable and his lives an hour away. I think now is a good time though, If I am going for my bachelors I will have at least 2-3 years depending where I stop or not before I get a job, I want all my kids to at least be in preschool before that happens. I think it is a good choice but other people's doubts make me doubt my own decisions. It doesn't help that all my husband has to say on the issue is "If it happens it happens, it is the kind of choice that has to be made for you." which really helped me a lot...not!