Getting fixed..?

We have two kids (2 yrs old and 1 yr old) and due in March with our third. We were using protection and tracking to avoid pregnancy and got pregnant, not upset but weren't planning on having all of our kids so close together lol but we decided to get fixed (my husband) with this child and it be our last. And lately I've been wondering what if in two years even we might want another. I mean our oldest would be four so it's not like we would be starting all over again. Financially we are fine even with me being a stay at home mom with our kids (which I have been for the last 2 years). Soo what to do about the doubts?