I have been there! Same thing, worked out twice a day, 6 to 7 days a week-lifting in the am then an hour of cardio after work-for 4 months. It was insane and totally impossible to keep up. I lost between 25 and 30 pounds doing it then I hit the wall. I couldn't figure out what it was. My diet was really strict-1400 - 1700 calories a day max.
So...I took a week off, I didn't go crazy with my food but brought my calories up to around 2400 - 2700 and didn't work out very much. (Maybe 5 times as opposed to 12 or 13).
After that week I kind of kept up the slower pace. Once in a while I'll hit the gym twice a day but it's more like 6 days a week now. I alternate lifting and cardio and spend about 90 minutes each trip.
It totally worked! My total loss is just over 50 pounds. I'll probably never drop that last 5 or so pounds - I seem to have a 7 - 10 pound range I move around in depending on what time of the month it is but I'm really at a great weight and size and if I did a body fat measurement I expect I'd be hovering around 20 - 22%.
My conclusion is that the closer you get to your goal the harder it is. When your body get's so used to all the hard work sometimes it just stops performing and you're overtraining. For long term maintenance it's hard to keep up a crazy workout schedule so eventually you'll want to find a routine you can incorporate on a regular basis in the future.
So don't beat yourself up-you've lost a lot of weight already girl!!! Just don't give up, you'll make it. Congratulations on the progress so far.