Newbie Diet

Hi guys, hope everyone is doing great. I have recently decided to start a cycle of Anavar/Test Prop to continue loosing BF. I was going to start today but, some of the other members thought I should do some more research and tune my diet before I start poking myself crazy. So here is the background I'm 28 5'7 200LBS i was 260-270 a while back and after a lot of dieting and a lot of working out have managed to loose a s**it ton of weight. But, lately it seems like i'm stuck I haven't been loosing any weight and I continue to diet and exercise. My current diet is ridiculous and overall painful. I started going to this weight loss clinic a few weeks ago and started Phentermine 37.5 1 per day and a B12 shot 1 time a week. This worked great for me in the past with a 500 cal a day diet but, My body and mind can't go through that diet right now. So i am at 800-1000 per day cal's, Still makes me feel shitty and 0 energy. IDK what my exact BF is what I do know is whatever it is I want it to be lower. I am determined to struggle and keep to my diet an exercise regiment but, need some help since I feel like i'm just wasting my time lately. Any ideas what I should do? Should I stop using phentermine? This stuff makes me super angry all the time, super depressed when I come down from the high and gives me insomnia like a MoFo.

TY