First time here/How to be honest with doctor/Where to start

Hi everyone,

I'm not sure where to start but I'm thinking maybe I have an eating problem. I flat out lied to my doctor today and it made me question why I did that, because I'm not generally a liar. 

I'm 23 and I've always been a thin person. In fact I've never had to try to lose weight and I've always considered myself very lucky on that point. My mom's also a thin woman. She's made it very clear throughout my life that I'm lucky to be thin and I should remain so. (I don't live with her right now though). 

Today I went to the doctor for an annual exam and she pointed out that I've lost weight (about 4kg, not much) since I last saw her a year ago. But I know for a fact that I had those 4kgs on me in December. (Well, maybe 3.5, if we say there's a difference between the scales.) 

She asked me if I ate enough and if there was a difference in my life and I told her I've been running twice a week and I eat well. This is not true and I just said it without even thinking. 

But I've been thinking today and I don't remember the last time I had three full meals. Do people even have three full meals? I don't feel very hungry. Just a bit hungry most of the time. I think on average for the past month I've been eating about once a day. Sometimes twice. Sometimes I just have a fruit or two for the whole day. I was thinking I was too lazy to cook - I don't like cooking. But I guess on the whole maybe this is not just laziness. 

Where do I start? I don't really feel like I need to eat more. I think I should, but I don't feel it in my heart, it's a rational thought. How do you start eating more? Do I need to tell the doctor? How would you even tell someone that? 

I'm sorry if this is too long