Assuming you would have naturally experienced one of the signs of ritual maturity, or bulugh, you become mukallaf. For a boy, these signs are:
1. Having a wetdream.
2. Growth of coarse pubic hair in private parts.
3. Reach age of 15 full lunar years.
As a result, it would be wajib for you to pray, and so if you know you did not pray for about two months, you are able to perform them as qadha`.
And Allah knows best.