Hello Yes of course you are underweight.
It’s not only healthy meals that matters But it depends also on the amount of calories you intake per day .also how much is your energy expenditure per day that also has to be monitored. As keeping all the parameters in mind a diet
plan is made which includes proper calories as per your energy expenditure along with the carbohydrates proteins n fats proportions being distributed in a way that leads to weight gain. Consult for detailed diet n menu planning.