This is really a serious concern, that you are not doing good in mocks. Because you also know that the left out time is less. And if you are unable to attempt the mocks properly it means your basics are not clear. So lastly, I would suggest you to start with topic wise tests and check where all you are still lacking then work on your mistakes and once you get a good grip on the same then start full length tests. But also consider that the time is less. Hope this helps!!!