Low sex drive

Hey ladies. This is my first time posting. I decided to post because I've been having a problem. I'm 21 years old and my boyfriend and I have been together for a year and a half. We used to have sex often. At least a few times a week. Around July I started taking an antidepressant that was prescribed for me. Now I have no sex drive. Maybe every two and a half weeks I want to have sex. Could that be the problem? My bf is so understanding and never pressures me but I still feel a little sad about it. Please help.