Trying to conceive.....

My body drives me crazy my period is never on time and I always have pregnancy symptoms but every time I wait to take s pregnancy test its negative, it's really causing me to be depressed because we've been trying for so long and I feel I'm letting my partner down because he wants it as bad as I do but it hasn't happened...he's more excited and picking up on things then I am sometimes!!!i feel I see and hear everyone else getting pregnant and I'm just over here waiting for the stork at my window?