Ttc for 13 months, normal tests

Tara • I was very lucky to get pregnant quickly for baby #1. However this time has been very unlucky. 13 months and counting
When my husband and I got married, we instantly got pregnant on the first try.  Then when my little one was 5 months old, I figured it's go time for baby #2.   Well 13 months later.. No baby.   I recently started seeing a fertility dr.  All the test have come back normal.   I am 35 and pretty 
healthy, but I am 25lbs over weight from where I started with baby #1.   I'm not sure if age and weight are fighting me right now, but I'm getting so frustrated.  Every month I get a negative result, I cry inside and sometimes in my pillow.  I know I should be grateful  for having one, but now that I want him to have a brother to grow up with.  I feel like I'm running out of time.  Has anyone experience being to have 1 child then having issues getting pregnant again?