My boyfriend thinks I'm developing an eating disorder?

I'm 18 years old, 5'8 and about 140-145 lbs. I want to be more around the 120-125 range. I've decided I'm going to try to eat around 1200 calories a day. Today I ate 1300 (and it was all healthy food pretty much) and I played tennis for an hour or two and played basketball for like an hour. Do you think I'm eating enough. My boyfriend thinks I'm developing a problem but I think this is how a person loses weight fast