Hello. Sudden changes , chronic stress, persistent worry about something,,,all this have a effect on our hormonal system and thus cause irregularity in our periods . Mostly it cause delay in it. This change in hormonal system also cause mood symptoms....this easy irritability is one of them along with frequent mood swings....all you need is to wait for your period ....if your symptoms persist even after that then you may have to consult a psychiatrist for evaluation..also it appear you are planning for pregnancy, so be cautious before starting on any medical treatment and inform about it to the doctor..... Take care