OK several things here. The most important that is highlighted is that she asked what your intentions were. She should have KNOWN what your intentions were. You have to make it clear, and the sooner the better. You have to set the frame that I'm attracted to you, I want you but don't need you. A MAN TO WOMAN FRAME. You failed to do so, and thus she asked, "What were your intentions?".

Now you are all needy and care a LOT about what she thinks. You messed up my friend. The initial lack of showing your intent messed everything up here. Learn from it and know that you have to show your INTENT unapologetically, regardless of what she thinks. It cuts all the bullshit out, and just gets straight to it.

Does this mean you have to verbalize it? No. You can if you want, but it has to be there in your vibe, in the underlying subcommunications. Girls can read them, and they know your intent right off the bat, so stick to your intent, stay congruent to it, and never ever apologize for it. Own it with complete certainty. This is the only way to truly get the girl.

Well to be honest, I don't know what I'm looking for, depends on the girl. She might be short term GF material but I want fuck-all to do with her kids. I don't know how the hell I tell her that without verbalising it?
I think I've fucked this one up now anyway, but it would be good for next time.

Then figure out what you want. It's as simple as that. Is it REALLY because you don't know what you want in a girl, or because you're too afraid to show her? Be honest with yourself here.

Maybe you're right. I don't have much experience with women but I've had a massive surge of confidence recently(lost weight, new clothes, new haircut, meeting lots of new people, realising MAYBE I am a desirable man), so it could be I want it all and I want it now and it's way too soon in the game to have realised what I even want yet.

Dude, you don't have to exactly know what you want overall right now at this stage for you. But you MUST know what kind of girl you want, what kind of girl falls into your spectrum of acceptability and fuckability. It's called having standards. Also you MUST know what you want with EACH girl. A goal. Do you want to get her number? Do you want to make out with her? Do you want to have sex with her. This is what I mean with knowing what you want. And then exactly this will be shown in your intent, since it IS your intent. And therefore you can show it and stay congruent to it and certainty and confidence and complete congruence will get the girl. It doesn't matter what exactly you want (hopefully to get the girl), but the certainty in what you want and what you are doing and not wavering in anything is what will get the girl. And for that you must know what you want. Therefore I urge you to find out what you want with every single girl from now on.