First let me say that I am so sorry that this is happening to you. No matter how long you have been married, whether or not there are children, and whether or not there seems to be drifting apart the request for a divorce is a shock to the person who is being told that the marriage is over.
We all change. Neither of you are the same person that you were when you were married. Every seven years, life changes. Think about the difference between a new born and a seven year old. A 14 year old and a 21 year old. There are also dramatic differences between 28, 35, 42, 49, 56, 63, 70, 77, 84, 91, 98, 105.
One of the good things is that you are young, healthy, and becoming slimmer every day. You can easily look forward to another 70 or 80 years of life. A lawyer told me that many people fall in love at 18 and by age 27 would have picked a totally different partner. That is the age when many of his clients came to him to start divorce proceedings. He said most were in happy second marriages by about 32 years of age.
As we mature, we are capable of making wiser choices. For now, get some rest, get some counselling, and take care of you. I know that this is not easy. If would be very helpful for you to look up the stages of grief. Divorce and death have the same effects on us. Here is a good site to start with http://www.livestrong.com/article/129455-seven-stages-grief-divorce/