You should try Wellbutrin. I was taking effexor xl 150 mg and after a few months I had no motivation, was gaining weight. Let me mention that I was the type of person that was so concerned about my fitness and would work out 5 days a week and then I couldn't do it. I couldn't do anything. My doctor gave me Wellbutrin XL and it made a lot of difference! Talk to you doctor about it.
I'm sorry you're feeling this way. I've heard that Lexapro is either great or terrible so if it's not great for you, please get off it and try something else. The lack of motivation is due to the depression but that can be helped by the right medication.
I don't mean to intrude, but your bf doesn't sound very understanding. If he is more concerned over your "classes" than you, you probably don't need someone like that in your life right now. He could be making this all worse.
Take care of YOU and that means finding the proper meds/therapy. Keep good positive people around you. Watch comedies - laughter is good for the soul.
Try Wellbutrin. It works on dopamine which is supposed to be linked to motivation. Unlike SSRI's it can actually improve your sex drive. I take it with Cymbalta and it has been and excellent drug for me. Good Luck!
I suggest you go and see your school councelor. I assume you're in College, correct? They will have a therapist or a mental health councelor. Remeber - your education is a long term goal, break it down to little ones, take it day by day - it'll be worth it, you'll get a good job, make more money, have more prestige, etc. If you think it's related to the meds you;re on - call your Dr. and tell him what's going on, he might prescribe something else.