Hooker seems great for you; but you want to start hitting the gym to build up strength. You don't have to be too fast or too strong as a Hooker, but you must master the technique of rucking and hooking, not to mention your work-rate would be the highest of any of the front or second row; Therefore you need a bit more strength and a hell of a lot more endurance. So here is what you should do; 1. Practice your set pieces: hooking in a scrum and throwing line-outs (line-outs are crucial) 2. Get in the gym and build strength, along with gaining weight (Doesn't matter how, could be muscle or fat for all anyone cares, as long as your getting stronger) 3. Do some HIIT (With sprinting or body weight stuff) to build endurance. All of this should be done outside of training sessions (for step 1 you can do in and out, you could just try and throw a ball around when your at home also)