Okay, then here is the reality of your situation: you already advised your intent to remain permanently in Canada, and I assume you're abroad to finish up family/personal/professional business. The truth is, your personal situation doesn't matter, you're Canadian, you have an OHIP card and received it before leaving the last trip, and when you get off the flight you'll be a resident of Ontario.
The fact you haven't used the card means nothing, when you come here you are incredibly unlikely to face any questions. Just go to the doctor, use your OHIP card when you permanently arrive back home in Ontario. Just make sure you have updated your address info with your new address, go online and use Service Ontario's online services. Health care in Canada is not based on your proof of income, it is based on your residency. When you arrive again, you'll be a resident. Some immigrants have a hard go of it and don't find income in their first years anyway (especially married immigrants that have little English, some live here for years without working or income as their spouse makes the income, they have health care services without question).
Some of the other advice you've read here is a bit alarmist, I wouldn't pay as much attention to it. But, out of an abundance of caution, I would make plans to arrive in Canada early and ahead of schedule. I would not recommend coming back to Ontario, then visiting the doctor the next day. Not because you'd likely face any consequence, but it would leave open more questions should questions ever be asked. If you work a temp job for a few months or weeks before you deliver, then all the better. Your several weeks of income would never even be questioned. You are a resident of Ontario regardless.
I am a bit surprised at some of the alarmist writings posted here, but you have my point of view on the matter. I think you can discern between these posts and I trust that you can read between the lines and figure things out. Best of luck to you! Welcome back to Ontario when you arrive.