I've got a few problems...

1) What to say. I keep getting myself in situations where i think too much in what to respond to people. But when i finally convince myself 'Just say what you want and be boss about it' i end up saying the wrong things. I'm also a bit of what you could call a slow thinker at times and find it hard to come up with responses and trust me if i don't think about what im going to say i go seriously uncool.. Has anyone had this before? Does anyone know a way i can overcome this?

2) I think to much on my appearance. Yes, i know this is a thing AFC's experience but i really am concerned about it. I'm starting to feel that i over think this too much but when i tell myself that well... nothing. I feel that its all about looking good and that i don't live up to these standards that girls want which really takes a shot for my confidence. For example, I have a slightly receding hairline and considering im only a student at 18 (in the UK) its not seen as a good look and it worries the shit out of me. At times i will also envy people i see who are considered as good looking and see them get all this attention and realise how much power they have. Any tips on this one?

3) Losing focus. This is not just during game but in everyday situations. I find it incredibly hard to focus on something and have this strange situation happen to me where i will be lost in my own mind. Crazy huh? But it is seriously pulling my game down and in fact my life. I'd would be awesome to hear from anyone who has has something like this or know how to stop this.

If i can sort out these 3 points i think i will see major improvements in my game. Too me, it seem that from this that i may be over thinking things but even when i tell myself to stop it doesn't work on times its like i have no control over my mind. But meh, i don't know. Could this just be a phrase in my life? Whatever. Any help or stories of similar problems would be awesome, thanks guys.

Yes, you are overthinking.
Start to simply not give the slightest fuck about anything other than yourself. If you'll start to feel good about yourself, that will be reflected in your behaviour.
Build a solid frame and stick with it. Say what you think and don't be afraid of the outcome. If it's the wrong thing, at least you know not to repeat the same mistake.
Make some friends and try to contribute to every conversation you have. That way, you can learn/develop your social skills.
Your appearance is not as important as your personality, so stop bitching about it. Try this. Go out for a few hours and ask every girl you see if they think you're attractive. You'll see that at least half of them will give you a positive response.
And last but not least, confidence.