I'm 21 year old female who has been experiencing weird symptoms for over a year now that seems to be related to my left ovary only. i'm worried that it can be ovarian cancer instead of an ovarian cyst. can ovarian cysts last this long?

Ovarian cancer would be extremely unusual at your age and highly unlikely to cause symptoms for a year in the absence of any clinical findings. Ovarian cysts normally come and go and are not a concern. There are various benign cysts that can be persistent but they are almost always asymptomatic. Simple less than 5 cm cysts with thin walls can be safely followed indefinitely if they are stable.