But I thought it didn't have enough calories to be good for building muscles, I even started to eat more because of that.
The question of weight, when simplified, boils down to this:
More Calories Than Needed = Weight Gain
Fewer Calories Than Needed = Weight Loss
So, when asking yourself whether or not you need to be eating more, ask yourself this: Do I want to gain or lose weight? Then ask yourself this next question: Am I gaining/losing weight like I want? If the answer is no, then look above and add or subtract calories as necessary.
I have a slightly different opinion of the diet from most others who have commented. While overall it may be healthy, some of the combinations aren't great (IMO). The food combinations don't look real good to me. I know a lot of people do it, but it's actually not good to mix fruits with other foods, and in fact some say you shouldn't even mix different types of fruits. While I prefer to not mix protein and carbs in the same meal, (which would be my other complaint) you may want to add in a small snack before working out. Something like a half a grilled chicken sandwich- the reason for this is the same reason I don't like to mix them - carbs and proteins require different enzymes to digest and the two don't really work well together. This slows the digestive process and prevents full proper digestion. From a purely healthy eating standpoint that's bad, but for purposes of working out, it's good, as with the digestion slowed, you won't burn through the protein right away, it'll be released slowly throughout your workout. The only other comment is a matter of personal preference, as I really don't like milk, and it looks like you consume a lot of it. Our bodies don't even make the necessary enzymes to properly digest any kind of milk past the age of three, and we don't make the right enzymes to digest cows milk at all. I prefer almond milk or soy milk, both taste better and are easier on the gut. I don't know what your salads look like, but you might also want to incorporate more raw or lightly steamed vegetables. Broccoli is a good source of calcium if you should reduce your milk intake.
One possible suggestion would be to look for a *well educated* personal trainer. One who has a good deal of education and training can help with your diet and will have knowledge of dealing with diabetes as well.