Good questions. Looking at him as being or having been a love interest and admittedly having been good to you.
If not together, romantically, is he still part of your social circles?
I ask, not in skirting how you question your future emotional health, but because it will factor in.
I take it, he's likeable, even if the thought of a future scares you with him?

If still circling (socially)around one another, I could imagine secrecy taking its toll.
if still circling I could imagine ostracism of a sort.

Depends.

If he's someone you may never see again, I cannot imagine secrecy eating away at you.

My grams younger sister, lived out of state one summer, helping a neighbor with their summer business. This was ages ago. This neighbor calls my great gram one day saying she'd stay the winter. Grams aunt died in her 50's from liver complications. Years later, gram and the family received a call from a woman saying she was adopted and sought us out.
That was a secret that did her in, grams sis. Honestly, grams mom would have understood. They all would have. She'd met a merchant marine, and got pregnant. But the neighbor was more of a hidden secret type.
In your case, look at the big picture of this man. What role is there in the future, socially, demographically.
If you keep it a secret you'll need a quiet support system.
Any family members you can talk with? Grams sis told no-one, that was the thing. Never went on to have any other children...

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