Major Plateu

Options
I am about to turn 30, I am 6' at 205-210lbs, with roughly 15% BF. I am very comfortable with the way I look, and consider myself an elite athlete. However, I am facing an issue that has never been present in my life. My line of work its very dynamic, one day I may be doing administrative work, the next day running 6 miles or the following hiking with a 80lb rucksack over biblical distances. Most of the time, its hard to control my diet since we mostly eat what we have and when we can. (by the way I am in the Marine Corps). Here's my issue, after putting my body through numerous body-slaying courses, some of these required me to go without eating for 2 weeks and still be able to function physically, also finning(open-water swimming with gear) about 3k, running 10 miles at about 7:00 min mile, ruck between 12-14 miles at a minimum of 4 mph. Basically, I have had the opportunity to take my body to its full potential. At the conclusion of September 2012, I concluded my latest course, which was aquatic in nature, and very physically demanding. Upon the conclusion of this course, I decided to take a week off, well, after that week off, I still wanted to rest, whenever I exercised I still had the stamina and endurance, but my body just did not want to function, it was unpleasant. I also gained about 8 lbs, which puts me a bit above my comfort level, but nothing too bad. I believe this was due to a combination of not a whole lot of cardio and eating whatever I wanted. Also, and I think this is one of the major issues, I am so used to thrashing my body and pushing it to its limit that whenever I don't workout like that, I feel as if I had not worked out and feel dissatisfied.(This may be a psychologial factor)

I am not sure what to think about these changes. Does it have to do with the fact that I am almost 30? Has anyone had this happen to them? Any pointers on how I should approach my training would also help. By the way, if there are any things I left out which makes it hard for you to answer, please let me know. Thank you.