I am currently studying History, Government and Politics and French at A-Level but I'm finding that I really dislike French as I feel very underconfident for it. I feel like my whole class is so much better than me and I feel like I'm not doing as well as I should be doing at this point even though my grades so far contradict this feeling? I got an A in GCSE French so I should be able to keep up with the work. If I were to swap it I think I would probably start English Literature, which I got a 9 in at GCSE, although I have never particularly liked English Literature and I have always enjoyed French.
Do I stick at French and hope that my confidence improves or do I swap to English Literature, where I'll also be a month behind, and strongly dislike but it was my best result at GCSE?
Swap! Do further research into other subjects! Do what you like
100% stick with French! You said that your grades so far contradict your feeling of inadequacy, meaning you're probably just feeling a bit insecure surrounded by new people who may also be good- your confidence will definitely improve as you move through the course.
Just because you did brilliantly at gcse literature doesn't mean you will for a-level; if you don't enjoy it then you will not work hard and come out with a much worse grade. As long as you enjoy French and you work hard at it then you will do well (as your A grade at gcse also shows ability) and your time at sixth form will be much better.
You could ask for a taster lesson? Though I'd recommend doing the subject you like! A Level languages are a huge step up from GCSE languages so it may some time to adjust.