Shakes and other "diet" foods are only temporary fixes. You will need to start eating properly, watching your portions and getting regular exercise in order to lose weight.
Since your looking to not interrupt your life with your boyfriend the best ways to lose weight are to change little things. Keep in mind since your not radically doing anything different don't expect pounds to rapidly drop off
Make a log of everything you eat when your not around him.
Switch out stuff where ever you can. Like switch M&Ms for bare celery cut up in strips for snacks. Wake up at work with coffee with 2 sugars or less instead of cola. Instead of fatty meals out that are not needed for social purposes change it to a protein drink like Muscle Milk. Keep in mind, meals out with friends are important for social interactions.
Incorporate exercise into your daily routine. Park your car on the other side of the parking lot. Better yet, park at least a mile away from work and just walk casually. That's 10 miles per week. Insist on always taking the stairs instead of the escalator or elevator in each and every building up to 10 stories.