Yeah, you definately need another cat, go for it!
But serioulsy, I also don't have advice to give. We have two as you know, and I'm glad about that, they keep each other company. Maybe 3 is weird number, I don't know. We are also planning to have more cats later (few years from now) and we will keep the number even, so everyone has friend... I don't know if this counts when it comes to you...