Will I regret having only one child?

Husband and I unintentionally got pregnant. She's now 6 months old and I don't know how I feel about raising her as an only child. Most strangers say we should have at least one more. My husband would love more; I never wanted the one (but feel blessed to have her and love her dearly - just didn't need to be a parent to feel fulfilled in life). IF we have more, I want them to be close in age so I feel self pressure to decide now whether to have more.