Maths A level is one of the hardest a levels there is, so it’s only natural that you’re going to be finding it tough. The jump from GCSE to A level is real, and if you haven’t done a further maths qualification it’s significantly harder. So firstly, it’s okay and understandable that you’re finding it tough.
I believe as soon as you realise this it’s easoer to work out whether the amount of difficulty you feel in this is normal, or whether the course is wrong for you. Maths isn’t for everyone, and that’s okay, it doesn’t mean you’re not smart in the slightest. I would say to keep at the course, as there are different sections and topics that you may like more and find easier, and that will give you time to work on your weaknesses. However, if the course is just making you more stressed and you can’t focus on your other subjects maybe it is time to discuss dropping it with your tutor/teacher.