have been eating too few calories all along?

Hi everyone! I have been using my new fitness tracker (the polar loop) with a heart rate monitor during my workouts and through using it have discovered that for the past 5 months or so I have been eating at a fairly large calorie deficit. I kind of had a feeling I may have been doing this, but was not sure until I purchased the loop. In the beginning I did loose some weight (around 8 lbs) and I am happy where my weight is now. The thing that is confusing me is that I have been maintaining this weight for a few months now, but my fitness tracker is telling me to eat more calories. I do feel hungry often, so I probably am eating at a deficit, but I don't want to gain weight if I start eating the calories my tracker is telling me I burn each day. However, I would like to eat more as I would probably feel better throughout the day. I have been eating around 1500 cals a day, and should be eating anywhere from 1700-2000 a day according to my tracker and depending on my exercise that day. If say, starting tomorrow I increased my cals to 1800 per day would I gain significant weight? Even if my tracker is telling me I burned it?