To get size you'll want to go up in weight, which will probably result in you having to go down in repetitions. Also, switch up what exercises you do/food you eat, because your body will become accustomed to doing these things and build a defense against it. You want to trick your body.
One thing I did while hitting a plateau on chest was instead of doing high weight, i lowered the weight and did AS MANY repititions I could do until I could do absolutely no more. Do a light weight and try and go for around 30+ reps. This shocked my muscles so the next time I worked out, the weight felt incredibly light, lol. I was able to go up in weight again after that. Try giving that a shot.
Also you'll want to do cardio on your off days to get definition.