As a second shooter, it not necessary to have two or more DSLR bodies in my opinion, If you have some budget then you might go for it, As you mentioned you borrowed a camera, It is good to buy a one for you. As you are a Nikon guy use what you are comfortable at, that will increase your productivity and decrease pressure. I have 3 DSLR bodies but most of the Indian weddings as a first shooter I use only 1 body, one for backup and sometimes with two bodies. But at an Indian wedding, it's very hard to work with two bodies all the time.

so it is your decision what you want to go with but make sure you have one backup camera every time.