My husband owns a property under his sole name. If I am going to purchase another property under my sole name, am I considered as first time buyer?

No, the first time buyer relief will be overridden by the higher rate rules. SDLT rules treat married couple as a single entity. This means buying a property under your sole name now would mean that as a married couple your husband and yourself would end up owning two properties. Hence, the higher rate SDLT applies.