Discouraged

I’ve been at burn now since March and in full honesty I’ve slacked with dieting and staying fully consistent but in July I hit the peak! Lost weight, lost fat and gained good chunk of muscle but since then I’ve been losing progress and now I’m the heaviest I’ve been in a hot minute, I even seriously locked in with my diet and running and going to sleep early and everything! And gained weight and lost muscle But when I don’t give a care I lost fat and gain my muscle back but still heavy in weight

My trainer says I know my body and what works….but I really don’t, I feel so defeated and alone in this struggle….any advice?