Will dropping my a level cause a problem?

I do Media studies, English Language and Law.
I didnt pick law, I was told to do it and now I barely have time to study for media or english. Law always takes up time and I don't even get the marks I studied for. For my mock, I got a U. Apparently I even misread the question or I would've passed but I just don't think its for me and I'm scared that if I drop it and pick up another a level, I won't get into university. What should I do? Should I like make a revision plan etc, follow it and keep going back and forth or should I drop it? because the thing is, if i drop it and pick up another subject, it's only half an a level I will get which might not be enough for what I pick at university. What should I do?