i need help

ok, this is my problem, I have lost about 20 games playing 2v2 with my friend, he is human and I am always Night Elf..... the enemy always over powers us by

A. Harrassing us and keep sending guys in our town hella fast
or
B. Have an army that just over powers us (about the same amount of guys just certain kinds of guys beat our army)

I dunno if anyone else has this problem, please help if you can