HI This Is Mona I Am 25 Years Old Female.

HI this is mona I am 25 years old female. I started having irregular heart beat about 4 month ago when I started school. I am on birth controls. The symptoms are not bad but it concerns me. I am a full time nursing student and under a lots of stress. I used to drink 2-3 coffee a day but I cut it down. Now I am drinking green tea.
I can hear and feel my irregular heart beat at night time when I am up studying. I only drink green tea around 9 pm to help me stay up during the night to study