keep yo yo ing

Are you having "bad" days because you aren't adding in the foods you want on your "good" days? Try adding in small portions (even half portions or so) of some foods you're craving. It won't break your diet and is much healthier than jumping up by hundreds of calories on bad days because you finally cave and give in to your cravings! Just keep going, stay strong and know that even while the scale isn't dropping rapidly you're making a POSITIVE life change.

Also, are sure your goals are good? A lot of people think they need a lot fewer calories than they actually do (I was one of them until very recently). Check your TDEE (see this post for help)
http://www.myfitnesspal.com/topics/show/512956-tdee-what-is-it-and-why-you-should-not-eat-below-your-bmr

Also, something I have found very motivating is a fitbit. The website (and you can link it to MFP) gives you daily goals to meet. Since then, I have been much more motivated to get up off my butt and meet my daily goals: 10,000 steps, 5 mi, burn calories of a moderately active person, be very active for at least some portion of the day and climb at least 10 flights of stairs.

And of course, the community side is really helpful. I, like you, have had trouble sticking to it but this time I have decided that I am GOING to lose the weight. Feel free to add me as a friend.