Chiming in here... at the tail end of what Hops' said, so succinctly...
"not ever having" is most definitely a loss... and your instinct to grieve this... spot on. And (I'm doing a lot of "supposing" here) I think not grieving this leaves a big ole' lump of obstacle that just gets in the way.
There is a layer of pain that surrounds the "not ever having" that appears to have all the characteristics of a black hole - but that layer isn't very thick - if one goes straight through that into looking at the significance of the fact - "I grew up without the benefit of __________." - and begins to place that "fact" into the context of one's self, JUST ONE characteristic of one's self, like freckles or the shape of one's eyes - then that one fact doesn't stand out anymore as insurmountable, as a curse, as a big secret, as something that will inexorably mark one for life. It is only one circumstance or condition of how you became YOU... and there are so many more, you know? As a child, it's easy to forget that today's woe isn't permanent. (yeah, that's one thing parents are for...) But we are sooooooooo much more than the significance of one individual fact about us.
But this particular loss does require being singled out, paid special very gentle and loving attention. I've found that I have to remember to honor my own loss of "not ever having"... so that I don't reflexively shrink away from connecting to other sources of the exact kind of maternal energy and deny myself feeling that now... claiming "I'm OK" - "I'm tough enough" - "I don't need this"... I shrink back, precisely because of that thin, intense membrane of pain that surrounds the loss. When I can let go and go through the pain - and just connect - it's like breathing fresh air for the first time.
Over time, that layer of pain has gotten thinner, less intense, and is fading.
Just go easy with this, GS. Cut yourself some slack - if you're ill it will only magnify the emotions. Give yourself a specific amount of time a day to address it - and don't set an expectation for when you'll be "done with it". Over time, all the different aspects or facets on the "lump of coal" will come up - each one addressed in turn; grieved; accepted; put into a new place - context - and then you'll notice that the coal has transformed into a jewel... that instead of blotting out all light & good, radiates it throughout yourself and your life.