I’m a medical registrar, 1 year away from consultancy. I love my job! Yes it’s hard, yes it’s knackering, but it’s so rewarding. As an OT, you’re already well aware of the working conditions in the NHS.
38 is not too old - the rotas will be more tiring than when you’re in your 20s, but the emotional toll will be easier as you’re more mature, with more life experience, better coping strategies and already have vast experience working in the NHS.
I would recommend a graduate entry course - Warwick University takes graduates only, so no one younger than 21. Most were in mid - late 20s upon starting, but lots in mid-late 30s. Oldest was 48. Swansea, cardiff, Manchester and peninsula also have graduate entry programmes.
If you’re passionate about it, go for it. Even if you get to the end of medical training and start working as a foundation doctor and HATE it, there are LOADS of careers open to you with a medical degree.
Where abouts are you based? Find a friendly junior doctor to shadow on call, see if it’s what you’re expecting and if you’d be happy to do that for 10 years!