breastfeeding and hormones?

Is it strange that I am finding myself very emotional and sensitive every since I've started breastfeeding ... Daughter will be 4 months on the 10th but I find myself really sad and start crying when I'm away from her at work .. Ive also noticed that when people will make jokes or play around I take everything to heart and sometimes start crying ...I know with breastfeeding your hormones increase (oxytocin and prolactin) but is this normal?  Anyone else experience this ?