Why am I gaining weight and not losing any while working out?

I've been doing traditional Shaolin Kung Fu for about 3-4 weeks now and I've actually gained about 5lbs. I changed the weight I eat drastically, I cut out all fast food from my life and started eating canned tuna and various low cal/low fat pre-made meals. (lean cuisine/weight watchers) I decreased my fat/cal intake and upped my protein a great deal. I quit drinking soft drinks and started drinking water, usually intake about 4-5 20oz bottles a day. My work outs usually include about 10 minutes of intense cardio, lots of sprinting and jumping. 10 minutes of stretching and about another 40 minutes of various Shaolin exercises. Sometimes we hold a certain position until point of exhaustion in the legs and then move to a new position and do the same. My thighs are usually on fire by the end of cl, so I know i'm working the hell out of the muscles. I normally leave cl drenched with perspiration b/c we are doing such intense routines. After cl I drink a smoothie with roughly 45g of protein and 5g of L-glutemine and take an Omega-3 fish pill as per a nutritionists advice to aid in muscle regeneration so I'm not so sore after workouts. I'm 5'10 and previously weighed 175, now I'm 181. Any thoughts?