We're all going to have different opinion, but mine is that you have two main problems:
1) as others have said, your body is adapting to what you're doing, making the exercises less effective. I've been working with a couple of different strength training systems (New Rules of Lifting for Women... now on to Power Training) and both make a point to change up your exercises quite a bit. Except for the break-in period of the first one you never do any set of exercises for more than three weeks. You've also go no recovery time in there. Even with bodyweight exercises you should probably do them no more than every other day.
2) I don't know the intensity of your workouts, but if they're high you're probably not eating enough. If they're not leaving you dripping with sweat and ready to collapse, that may also be your problem. However, I'm definitely not suggesting that you do those kind of workouts 6 times a week.
Here's what I do:
3 days a week - strength training - 70-75 mins at the moment
This is a mix of bodyweight exercises (push-ups, get-ups, hip extensions) and ones with weights (bent-over row, dumbbell press, dumbbell snatch, deadlifts). When I'm done these, I'm done. Each time I do them I try to lift heavier weights. I used to do things like dumbbell curls (I could probably do 100) with light weights. Honestly, they did nothing for me. Oh, and if you can do 50 girl push-ups it's time to try full push-ups. Even if you can only do a few.
On these days I eat 2300 calories.
2 days a week - cardio - 60 mins at the moment - some weeks might be 3x45 mins, my schedule is changing
This is either light cardio (walking) or higher cardio depending on mood, energy level, access to equipment. Last week I used the college gym and ended up with higher heart rates than normal. I really don't aim for really hard cardio. It's usually only slightly more aggressive than a gentle walk. When I use my treadmill at home I'll do 2.5mph at about a 5% incline. When I walk outside it will be a combination of walking with some very light jogging thrown in.
On these days I eat 2150 calories.
2 days - rest days
No formal exercise these days. Now, these aren't usually veg on the couch days. Last weekend on my rest day I cleaned and cooked a meal for company. On my lifting day (Sunday) I made jam. Normally I leave chores and errands for my rest days. However, rest days are important. It lets me put more energy into my workouts.
On these days I eat 2000 calories
Give or take we're about the same weight. Although since you're posting in the 20-somethings I'm possibly 20-years older than you are (I'm 42). You should be able to eat more. A couple of years ago I was in the same situation as you were. I was eating probably 1700-1800 cals a day, doing 5 weeks of excessively hard cardio, and doing a job where I was on my feet all day. I went months with little to no weightloss. All I did was drop my calories which didn't help at all. Combining that with ignoring warning signs of illness ended up putting me in the hospital.
So my advice is STOP.
Either increase your calories, or lower your exercise. A good first step might be to take a week off from the exercise. Eat 1500-1800 and do nothing but daily movement. At the end of the week start into a more balanced exercise program, but increase your calories slightly. Every 6 or 12 weeks consider taking a break.
Interesting point, but 9 weeks ago I did no exercise, ate 3000 cals a day, and gained only one pound. The week after I lost 5.4 pounds. I will be doing something like that again in 3 weeks. At this point I'm not suggesting that for you, but try a rest week with the same level of calories. It's worth a shot. Good luck.
Added - duh, none of this is any good without results. I lowered my calories on Sept 1st (was doing a straight 2150/2400 for rest and/or exercise days since the end of May). May 25th to Aug 31st - lost 29.6 pounds (~2.1 pounds per week). Aug 31st to Sep 14th - lost 4.6 pounds (~2.3 pounds per week), although obviously that last number is based on a much smaller number of weeks, so it may change. The main point I'm trying to make is that you really do need to fuel your body when you ramp up the exercise.