Weight is being weird

Hello, I’ve been on a weight loss journey for 3 months now and currently down 18lbs from 178 to 160. Some context, I am a 22year old 5’5 male, and am trying to get to 145lbs. I’m on pretty strict deficit and am exercising 6 days a week (30min cardio, 1hr weight training). My situation is that when I do eat a lot like for a day I gain weight very fast like 3lbs. I get that it’s normal for weight to fluctuate but the weight hasn’t seemed to have disappeared. I’m afraid that after I reach my target goal, the weight will come back very fast even if I keep my meals in check with occasional cheat days. Any advice?