I didn't read all the replies cause I'm studying for an exam tomorrow, but if you want to lose weight (seems like what you want to do from what I've read), and gain/keep mass, you don't necessarily need to supplement protein, but just EAT more protein and fiber. You'll feel fuller, and you'll get the amount of protein you need.
I take protein shakes, but only on days that I 'feel' as if I haven't ingested much. I don't train for bodybuilding, but just for general fitness, and sports.
My suggestion is, just get a few snacks which are full of protein, such as cottage cheese (protein) & fruits (fiber in most of the peel), almonds, peanut butter, etc etc. Add some Tuna to your diet too if you like the tastes. I love it, and its full of protein.
General rule is, to keep muscle mass, you need 1.6g of protein for every kg of body weight, and if I remember correctly, 1.8g/kg for sport-performance muscle building.
I don't calculate everything, and I just go by "feel." If I 'feel' as if I haven't eaten much protein (too much rice & bread, not enough fruits, veggies, eating processed foods), then I'll take a protein shake, or a protein bar. I guess you just get used to it after a while, but really just try to calculate how much you normally digest in a day.