I got into a slump like that for a few months! I was deligent on working out at least 5 times a week, and then I hurt my leg and was like F it lol and didnt work out for months. Thankfully I didnt gain anything. I maintained. But i noticed my muslce that I had kinda deminished, and it was just skin. Its just a a matter of getting motivated again. Sometimes Its hard, but it will happen, Just say I WILL do 30 mins of cardio today. I will lift my weights or hit the gym. I honestly dont go to a gym. I have free weights in my basement that I use for my strength. and I download workout videos Ex turbo jam, turbo fire, p90 x etc. Or i go roller blading with the dog, or for walks with her. Im going camping this weekend, so weights and roller blades arent accessable, but i am going to go for long walks around the campground, go for hikes, walk to the cliffs instead of drive. Maybe use the water and do some body resistance training in there like squats and tricep dips. Its easier but still works. Long as you are moving you are burning ! You will get out of the slump