My Weight

Well I just came from the doctors and my weight is the cause of my problems, I have tried everything to lose this weight and so far the only thing that has been consitant is the fact that I will lose 5lbs and put it and maybe 2 more pounds back on, I told my doctor this and she said that I am losing the weight to fast, I never knew that 5lbs a month was excessive weight loss, she says 2lbs a month is normal...but if I am eating right and working out and my body lets go of 5 in a month isn't that normal for MY body and maybe not excessive? I am just wondering because I am becoming so frustrated with the whole thing........and what does she think is going to happen when I take in 1800 calories a day and workout my body is going to let go of the weight and it maybe quick in the beginning and then slow down as I get close to reaching my ideal weight. I also told my doctor that I have no energy to continue my workouts and I wanted to know if she could give me a B12 shot or B complex something, her advice to me was to get a multi-vitamin and Vit D and take that everyday and she thinks that will help but when? I have been battling with my weight for 5yrs now and nothing...I have never weighed this much and what little bit of weight I have put on over the years was easy to take off whenever I got active, so now what is the problem? I am really just ready to go the diet pill route and energy drink and call it a decade...... I mean what else can I do?