I am able to solve only 7-8 quant questions out of 23 during a full length mock but afterwards solve 13-15 questions without the pressure. How do I improve my score?

keep giving mocks. After mocks you are not afraid to try different approaches and there is no time pressure , in mocks we all want to approach questions in ways we have practiced and that might not be the best way to solve that questions.You give more mocks, become calmer and more confident in trying different approaches than what you have practiced . I am facing the same issue and this was my analysis.Hope it helps:)