Hi,
I know exactly how you feel rn and it is the worst :/// The same thing happened to me last year (I'm in year 13 atm) but with geography. I hated it so much and I just couldn't face another year doing it- this was a combination of my teacher, the spec and the exams. I only fully 'realised' this in April of last year because that's when my intense revision for AS exams began and as soon as I started feeling this way, I went to my teacher and the head of tutors in my college. Long-story short, they said they could do nothing for me and that I either had to continue with geography or choose another college (to my horror!).
This was a huge disaster because I knew I was definitely going to go university and therefore needed a minimum of 3 a levels to apply. Again, long-story short, after thinking for ages, I found a solution. I am Arab so speak, read and write in Arabic and Edexcel does Arabic Language as an A-Level SO my plan was to do my AS exams (my college makes us do the external AS exams which means that if we are doing four A-Levels, we can drop one of them in A2 and get a qualification out of them) in my three current subjects (maths, chem and geo) and try my best to ace my geography so I could drop it and have a separate AS qualification in A2. Then, pick up Arabic in A2 and do an intensive 1 year course of both AS and A2 work (someone I knew was doing this at a Saturday School in a centre).
Anyway, I managed to get an A in geography for AS which meant I had a solid result to put on my UCAS and then I dropped geo. The college weren't happy about me dropping geo and doing an A-Level outside of college but to be quite frank, it's not really their problem. To fill the hours I am not doing in college, I have filler sessions where I can do whatever work I need to. So by the end of A2, I'll have 3 A-levels in maths, chem and arabic, an AS in geography and EPQ (something I picked up this year.).
Now, I'm aware you will probably not be able to pick up a language like I did BUT I might have a solution. Something I tried with my college but didn't push at it because of my Arabic A-level idea- persuade them to let you drop psychology then pick up a 'lighter' subject like Religious Studies or Sociology that you can take both AS and A2 classes next year . This will require a lot of work and mean that you are cramming a two year course into one year in addition to your other A2 subjects but that's what you'll have to do if you really don't want to carry on with psychology.
This will only work if you truly beg and tell them that you just can't continue with psychology and can't drop it because you'll need three A Levels to apply for university. But ideally, you need to decide right now whether you want to go to uni as you mentioned that you weren't sure yet.
**NOTE: Not all unis need 3 A-Levels. Most of the Russel-Group Unis and certainly Oxbridge, require 3 A-Levels, but many unis nowadays look at how many UCAS points you have so that could just mean doing your AS psychology exam and dropping it next year then picking up EPQ or another AS next year. Again, you really need to decide whether you want to go to uni now and then proceed accordingly**
Hope this helps and please ask any questions if you are confused or need further advice