You can be fit and healthy but you're soon to hit menopause, after which a lot of risks go up sharply.
Just to point out:
Routine mammograms for breast cancer start at 50
Routine bowel cancer screening 54
For people aged 25-49 they make up 9% of cancer diagnoses. 50-74 makes up 54% of new cancer diagnoses.
Princess of Wales is very fit and healthy and was diagnosed with cancer at 43 (probably a couple years later if she had had to go through NHS channels though). My boss who ran a marathon last year was diagnosed with bowel cancer on his first NHS screen at 54 just after Christmas.
You could have a baby at 45, totally healthy, and live a long and happy life until you're 100. You could try get pregnant at 45 (at which point miscarriage risk is over 50%), have a profoundly disabled child you're sole caregiver for, and be diagnosed with cancer at your first mammogram at 50 when they're 5 years old. You need to strongly consider impact on your existing child, who would care for them should worst happen.
Consider whether the loss in your life you feel is because you actually want a second child now, or the lingering grief of the DV relationship you were in and the parts of your life you imagined you feel that robbed you of (family unit, stable upbringing for DD1 and wanting a do-over, being able to have a second back then).