Low predictions will prevent you from getting a lot of offers. However, you need to speak to your teachers and find out what they're prepared to predict you before you start worrying about not getting into university. Different teachers and schools will have different levels of leniency but your motivation in lessons will work in your favour, as will any decisions to retake. Remember you can retake modules (it might give you a heavy work load but will be worth it if you put in the work) to boost your grade. If you can secure good predictions, you should be fine.
It's really not as bad as you think. Assuming you're dropping one of the D subjects, the grades that your predictions will be based of are ABD - only one 'below average' grade. A and B are both very good and can set you up for potential predictions of A*-Bs depending on your UMS, retakes, motivation for this year, and your teachers.