I'm still new, as I only recently started thinking I was polyamorous, and my gf of 5 months is aware and okay with me dating other people and it's really healthy between us. My question is, do polyamorous people NEED multiple partners? I'm okay with just having one partner, but I would rather have two or three. Is that still normal, or at least not impossible?
Polyamorous people don’t “need” multiple partners, because no one fundamentally “needs” a romantic partnership to survive. We need air, and food, and water, and sleep, and things like that.
But that’s a bit of a glib answer. Technically monogamous people don’t “need” partners either, but many people’s desire to be partnered is strong enough that it can feel like a requirement for a fulfilling life. There’s an entire media genre centered around the ways that people seek romantic partnership to meet a perceived need in their life!
Some people “need” certain things, not to survive but to be happy. Some people find that their most fulfilled life must include raising kids, or being able to express themselves artistically, or living close to nature. For some people who are polyamorous, it may certainly be that their best life can only be lived by being in multiple partnerships. Whether this is a “need” is ultimately a question of semantics.
Given the other details in your question, it doesn’t seem like this is a hair you need to spend much time splitting. If your partner is okay with you dating other people, and things are working in a healthy way, does it really matter whether this is something you’d be unable to live well without, or just something you really want? It doesn’t matter how “normal” your experience is - it’s your experience, and the only person it needs to work for is you!
You also answer your own question there when you say you’d be “okay” with just one partner, but “would rather” have two or three. You sound pretty self-aware that you know what it would take for you to be in a relationship that you are “okay with” vs one where you get more of what you want. You have all the information you need, so just keep on doing what you’re doing.