No, you've got it the wrong way round. ILR (indefinite leave to remain) comes after FLR (further leave to remain). Right now you've got leave to enter/remain as a student, and you want to switch to further leave to remain as a spouse. Once you get married, you can apply for FLR(M) at any time, provided you meet all the requirements. You'll be granted leave for 2.5 years, after which you have to apply for another 2.5 year FLR(M), and then after 5 years you can apply for ILR.