Feeling weird!

Hey, so I am a day late to my period. I'm anxious and curious about maybe being pregnant. I've been feeling sooooo different the past few days. 2 nights ago I was just so calm and go with the flow. It was weird, even my boyfriend mentioned it to me. Lastnight I just kept venting about my long day at work and I was super irritable. This morning, I almost called into work because I'm still so irritable, nothing wants to fit me, I'm itchy, hot and nauseous and stomach aches (like gas). I took a first response test yesterday afternoon and came back neg. I'm just curious if any women have gone through weird emotions as soon as they got pregnant. If so can you comment what you felt. Thankyou!