FWIW, I've had that basic problem in the past (multiple physical issues that could be exacerbated with lifting) minus access to a trainer, and have previously managed to increase my strength substantially just by taking it slow and if something causes the bad sort of pain, not doing it again. I haven't ever been able to lift my own body weight over my head, but I probably could get there if I didn't keep getting interrupted by injury/illness/life stuff/failure to work out consistently.