Your priest's advice is sound. Especially, since you live at home with your mom, following the rules of abstinence (from meat, dairy, etc.) strictly may not be practical. But you can always reduce your portions (stop eating when you are still hungry). And the most important kind of fasting is always available to us:
For the honor of fasting consists not in abstinence from food, but in withdrawing from sinful practices, since he who limits his fasting only to abstinence from meats is one who especially disparages fasting.
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Do you fast? Give me proof of it by your works. If you see a poor man, take pity on him. If you see an enemy, be reconciled with him. If you see a friend gaining honor, do not be jealous of him. And let not only the mouth fast, but also the eye and the ear and the feet and the hands and all members of your bodies.
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And so I desire to fix three precepts in your mind so that you may accomplish them during the fast: to speak ill of no one, to hold no one for an enemy, and to expel from your mouth altogether the evil habit of swearing.
And some more good patristic quotes:
"It is not suited to everyone to follow a severe rule of abstinence from everything, or to deprive himself of everything which can serve for the easing of weakness."
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"One should make use of food daily to the extent that the body, fortified, may be the friend and assistant of the soul in the practice of virtue. Otherwise, the soul may weaken because it is exhausted."
Once two brothers went to visit an old man. It was not the old man's habit, however, to eat every day. When he saw the brothers, he welcomed them with joy, and said: "Fasting has its own reward, but if you eat for the sake of love, you satisfy two commandments, for you give up your own will and also fulfill the commandment to refresh others."
