It really is a matter of individual circumstances, in my humble opinion. Why must an illness loom large, like a weight on your shoulders? I believe there's another thread here, where I mentioned that when both sides are laying everything out in the open to pursue a more serious involvement seems most appropriate. Because at that point, transparency is a key element of trust.
I was fortunate in that all relevant mh matters were before both of us pursuant to involvement. I'd toss in a bit of caution in listening and or telling since depressive souls can be prone to more self depreciation than is truly necessary.
Hope when the time is right for you, it feels matter of fact in revealing of yourself and they accept you with open arms and an open mind.