Hi Opal, everyone is on their own timeline as far as working about how they may experience arousal, so your age is not the most important factor here. As Heather mentioned, putting pressure on yourself (which can include thinking you need to have experienced certain things by a certain age), can have an arousal inhibiting effect, as this causes stress, which is a big inhibitor of arousal. This isn't to say of course that this isn't frustrating, or that you will automatically feel better hearing this, but please let me reassure you that this is something that many people experience.
Perhaps focusing on doing things that bring you non sexual pleasure, joy and fun could be a great way to feel some positive things around your birthday? Be that having a warm bath, being out in nature, wearing some clothing you like the feel of etc. whatever works for you, these can be ways to connect with yourself and your body in a nonsexual way. How does that sound?
If you're interested in how your brain works with arousal (and why taking the pressure off for now is a good idea) you can check out these articles: