Size, while beneficial, doesn't matter too much. In my team the openside flanker is 6'2 and about 78kg, but the blindside is 5'6 and about 66kg. As long as you can tackle with good technique it's fine. You do seem to be a little light, though. I'd advise bulking up with lean high protein meats like turkey, chicken and beef, as well as protein. Do weights as well. You can find bulking programs on Youtube.
You seem extremely undersized man. I'm 16 and I'm 6"3 and 194 lbs you need to bulk man.
well im 16 play u19 I play open side flanker and am 5'2 and 115 pounds size is not a big issue
What level are you playing at? I'm 5 foot 8 and weigh around 140lbs.