What do you want to do after A Levels? It may feel a bit early, but what you take at A Level could limit what you can do a degree in. I see your interested in science, so if you're thinking of a science based degree you pretty much half to do 2/3 of the core sciences.
I'm more of a essay based/creative person myself, but I have friends who do/have done Bio/Chem and found it incredibly difficult. I think they're subjects you have to be good at, enjoy and have full commitment to in order to be successful. You seem to be on track for good grades so I don't see any reason why you shouldn't take them.
Psychology is quite science based, but there's a lot of content to learn that might take away from your focus on Bio/Chem should you take them. I don't do Psychology, but I've seen what you would learn and it's pretty interesting.
I've just finished Media Studies (best decision of my life) because although the practical making of stuff is long, tedious and frustrating, it's not that difficult to do well in it. You said you've taught yourself how to use photoshop - you're already half way there. I had no experience, just followed the brief and got an A in both my AS and A2 coursework. The essays aren't too bad, if your on my exam board (OCR) in the first year you watch a video clip and talk about 'what you see' with media language then write an essay on the film/video game industry, then in A2 an evaluation of your work/progression and an essay on film/video game regulation.
I would say take Bio, Chem, ICT/Business and Media then drop one after the first year.
Look at past papers and see if what they're asking is of any interest to you - there's nothing worse than being stuck in a class you don't enjoy for a year.