flyhalf
wing
wing
right wing
utility back
Foward
it depends if you are good at catching if you are I would say fullback
The best position is fullback or winger, in which both positions requries the players to be fast.
fly half, scrum half or full back
Its appears a utility back but a good coach will advise you of the best position at this time
At your height i would reccomend scrum half or fullback you are simply not tall enough to be able to fend off anywhere else due to your height it is not un-common for 6 foot 7 second row's!
number 8 or centre may be a start as you are still growing at this age and therefore you may change body shape which in turn might drive the position you play
most 14 year olds are still growing so a definitive position can be difficult to pin point but in general, looking at the weight a position in the backs may be a good start until speed, ball handling and agility are established.