I would NOT be concerned. STOP TRYING!!! Seriously. The stress you are putting on your body is enough to make it turn into the "fight or flight" and it's in flight mode.
I say this from someone who tried for FOUR YEARS to get pregnant the first time and then was pregnant for five years in a row. STOP TRYING. Have sex for fun....nothing else but fun...don't worry about getting pregnant...you aren't using any precaution or birth control so just HAVE FUN!!!
This will happen when your body is ready and not a minute before. If you run off the to the OB/GYN - you will get a "label" on you - is that what you want? Oooohhh...PCOS....post infertility or something else. Your body isn't the same after your first baby....
I GET your stress. I UNDERSTAND how you are feeling....instead of trying to keep up with your best friends - be happy for them....just have sex for fun!!!
RELAX!!! PLEASE!!! PLEASE!! PLEASE!! Cannot stress this enough! Stop using the sticks and watching your cycles. just have fun.