hope this helps xx
I would strongly recommend against doing 4 alevels. No uni ever asks for 4, statistically people do much worse than 3 alevels and AAA looks a lot better than AABB.
It depends on what you want to do. Psychology and biology complement each other very well (especially if you go to study it at uni like I did). If you’re not interested in the subject you WILL NOT do well (you won’t have the motivation or mental strength to study the subject to the extent you need to to do well). Chemistry and maths complement each other well, however they are both VERY difficult and a huge step up from GCSE. If you didn’t get an A in chemistry GCSE don’t do it, and if you didn’t get an A* at maths GCSE don’t do it at alevel. (This was the guidance our school gave us based on statistics from previous years, and having done both myself at alevel and subsequently dropped them for being too difficult I agree. I got an A at maths GCSE and alevel was still impossible).
I’m choosing my A-levels and I’m unsure about whether I should do Maths , Chemistry and Biology by themselves or if I should do a 4th a-level and add phycology as that’s something I’m also very interested in. I’m just a bit worried about doing phycology and maths Chem and biology are apparently very hard and I’m not too good at English so I don’t know if the psychology exam is writing heavy
Also I'd recommend looking up past papers & what topics you learn about in psychology so you get a better feel of it to see if you're definitely interested.
Good luck! xx