4 months TTC and AF shows up again

Maybe I just need to vent it out but I feel so sad atm and tired of seeing people around me getting pregnant at the first try or by mistake.

Im 32 and we have been trying for 4 months now. I thought stress was the cause of us not getting pg as every month something happens at work and I stress about it but this time we were away, at home, on holiday and we were so relaxed and happy and yet Af showed her ugly face today. What am I doing wrong?!!