You don't even have the minimum number of GCSEs to be studying A Levels so unless there is exceptional circumstances it is not suprising that you find the workload for A Levels to be very high.However dropping out is unfortunately not that simple, and getting a full time job with no training (which is why apprenticeships are fine) is unfortunately illegal as everyone must be in education or training until they're 18 (not 100% as to whether this is 18th birthday or end of academic year in which you turn 18).
There are also options other than work or A levels such as an apprenticeship, or a different kind of college course such as a BTEC, however as you only have 4 GCSEs you may struggle to be accepted onto level 3 courses, so you'd probably be better off looking at level 2 courses that have the opportunity to continue into level 3 after completion.You can definitely retake GCSE Maths alongside an apprenticeship or college course and will be required to do so if you have achieved lower than a C.