Feeling tired

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I'm into heavy strength training and started cutting 3 weeks ago. I used a few calculators to measure my maintenance calories (2100), but scared of losing muscle so I only cut down to 1700 cal. I have a physically demanding job, do fasted cardio 3x a week + university. I'm worried I'm consuming the wrong amount of calories as I'm feeling very fatigued, yet I haven't lost weight. Please help!