When on my period, i have constant mood swings, depression, i understand "pms" but i feel this is a lot worse. could i have pmdd?

That is possible.: With Premenstrual Dysphoric Disorder (PMDD) a woman’s symptoms can be so severe that it interferes with her ability to function. It would behove you to seek mental health evaluation. Take care.

That's still "pre-": Whatever, whenever it is - you seem to feel that it is linked to your menstrual cycle - right? This would mean that the other half+ of the month you are no more depressed or hi/lo than the next person - right? If so, take this to an OBGYN and be patient as they run lab tests, etc. If it's as I've asked, try to avoid psychotropics. Talk therapy might help w/ mgmt skills but chemicals may be a risk.