Relationships are complicated, those of both the romantic variety and the mundane. They are prone to warp and twist under strain, especially when the relationship itself is new and both members are trying to find their midway point together. 
Why am I saying things that anyone who has ever been in a significant relationship knows? Because most people pass up the easy — albeit controversial — way to dodge those issues cascading into each other: not telling people about your new confidant.
Think of it like winning the lottery. That massive influx of change upends everything and no one knows what to do with that chaos. You get excited. You show off. You get too cocky with too much of a good thing. You squander it, and when you lose it, everyone knows you lost it.
Allow me to introduce the alternative. You meet someone, talk for a couple of weeks, go on a few dates, then make it exclusive. Congratulations, now do a “Romeo and Juliet”. Do not go and yell it from the rooftops. Do not advertise it to the whole wide world. Do not start building up the expectations of everyone you know. Keep it low key, or better yet, a secret.
Keep things simple. Let both yourself and the other person mellow out. Find out where you both sit once the inherently performative attitudes of an early relationship fade. Learn the ins and outs of each other’s preferences and personal avenues of communication.
You might think you delved those depths in the early stages, and you might even be partially correct. You may be glimpsing the outermost edges of who the person you are in a relationship with is, but there is no shortcut to knowing the ways they communicate and the little bits of themselves that shine through in certain situations. It just takes time, and that’s hardly an original idea. Mark Twain said, “No man or woman really knows what perfect love is until they have been married a quarter of a century.” Twenty-five years is excessive, but for the purposes of this discussion the point remains: it takes a while.
Outside pressure threatens to collapse a relationship as easily as strain from the inside, and the more people know in the early stages, the more likely that is to happen. How many people in your life do you actually take advice from? Not just listen to, but actually follow advice from? Few, I bet.
The more people you tell about your business, the more people who share their opinions. You may not even realize when outside influences are tainting what could otherwise be a great dynamic. According to Gwendolyn Seidman, Ph.D. with Psychology Today, even when we are satisfied in a relationship, negative opinions from our peers can affect our thinking. Naturally, it has a higher effect on some people, especially people still in high school or of similar ages, but there is always an unconscious effect. 
This is not just some hypothetical situation, either. I do not know if my relationship would have been what it is now had either of us let slip early that we were together. We kept it a secret for upwards of a year and grew together before anyone knew. We still learn new things about each other every day. 
Keep things under wraps until the situation has stabilized, and keep the best stuff to yourself. Trust me.