How do I get in shape for kickboxing?

Right now I'm 128lbs, my measurements are 38 1/2in, 37 1/2in, and 39 1/2in. My body m index number is 26.7. I'm 4'10" tall. According to that wrist tes,t (where you wrap your middle finger and thumb around your wrist) I have a medium frame, BUT I did weigh 100lbs this time last year and I was pretty healthy. I started weight watchers last week and I have been drinking a lot of water and walking everyday. My ultimate goal is to be able to run two times a day, and to be able to sign up for one of the Mixed Martial Arts or Kickboxing cles around here. I used to be really thin, I was wearing size 0 pants. I got on birth control and I'm not sure if it just made me hungry or what but I gained 40lbs in 8 months (1 school year). I'm off of it now and so I need to figure out something. I don't have any weights here and that protein powder crap makes me throw up. I don't want to be bulky! I just want to get the extra weight off of me and get a lot of lean muscle.