How long have you been attempting to break back into your prior levels of mileage and intensity? It’s really hard, in my experience, not to just dive straight back into it after years away and several weight fluctuations etc like you’re describing. It feels like you should be able to just pick up where you left off, but of course it doesn’t quite work that way. For me (I’m a guy in my early 30s, so different context and circumstances) it really required a full 8-9 months of 20-40mpw mostly easy running before I was able to build back all my strength and resilience to get into hard marathon training at 50-70mpw with workouts and re-approach some of my prior PRs. If I could recommend anything it’s to be patient with yourself, just focus on running easy 5-6 days a week, ignore the idea of racing for PRs anytime soon, and resist the urge to ramp up mileage or intensity before your body is ready. So boring and so frustrating, but for us mere mortals it’s not a phase of rebuilding fitness that you can shortcut.