Is he too clingy or being too serious too fast? Can you define what you mean by space? Are you introverted and need lots of alone time to recharge?

I don't see the problem. Asking for space isn't "breaking things off". It's just asking for space.

Depending of course on what you mean by "space" and what he thinks you mean by it.

As @LiterateHiker points out, you need to be clear on what you need before you can begin to communicate it.

Be honest but figure out what you need or mean by needing space .....and explain that.

Yes, I know that feeling... we all need our space. We need time to ourselves. If he is constantly around, maybe being straightforward with him about you needing a little breathing room will help. Or he may take it the wrong way; guess it just depends on the delivery.

What do you mean by "I need space"?

So you can be clear with him, it's important to figure out what you really need.

1. More time to yourself?

2. Need time to process your interactions?

3. Feel rushed, like he's pushing you too fast?

4. A chance to read, take a bath, clean your house?

5. Spend more time with your friends?

When you say you need space, do you mean you're seeing too much of him? Then just be as nice as possible and tell him you need to slow down a little and keep seeing each other, but cut back how many times you get together during the week. Just be honest and tell him you need a breather but still want to be a couple.

As a guy, I know I appreciate honesty as long as it's in a nice way, compared to long silences and having to ask (or guess) what's wrong, then watching things fall apart, when it could have been solved early on.

Yup. Be honest.