If you're not enjoying it now, you probably won't enjoy it at A-level. I enjoyed Chemistry at GCSE but when I did it at A-level I hated it.
Of course, this could be because there was only 1 other person in my class (who I disliked) and I hated my new teacher however I do also think I just didn't enjoy the content as well. Perhaps look at the chemistry A-level textbook and spec that your school uses and see if the topics are of interest.
What are you thinking about going into? If you don't need chemistry for it then I'd say change it. What are you considering to change it to? I'd say something like maths would compliment the other subjects nicely.
If you can, maybe take 4 including Chemistry just to test it out for a bit and then if you don't enjoy it then drop it and keep going with three