So...Calories..

I'm a Vegetarian, so most of what I eat IS vegetables. (I have eggs and milk as well because they are naturally produced) I've been rather good about logging all the foods that I eat, and I exercise three times a week.

What I'm concerned about is that fact that my target calorie amount is never met, I keep getting told that I'm not eating enough and that it can put my body into starvation mode. I don't think I'm doing that as I eat three times a day and I generally have a snack at some point. I realized on most days I eat about 1000 calories to maybe, maybe 1200 if I'm going to the gym that day.

I'm wondering if I need to eat more to help my body loose weight (i'm guess I weigh about 160 ish as I haven't got a scale yet I really don't know) I started dieting quite some time ago (last January and started at about a size 18 now I'm at the 12/13 range) and I've maintained a 3 times a week gym schedule. I think I hit a plateau about a month back but then I started using the my fitness pal (on my phone first, now online too) and I've started loosing some more weight now that I'm eating more.

I'm just kind of confused about this, as I don't eat many things that are high in calories, yet when I log for the day it tells me I'm not eating enough, I haven't exactly changed much in my diet either.