Infertility has a fourth thing
If your strand is infertility rather than a single loss, everything above applies and one more thing sits on top of it.
There is no date. Nothing happened on a Tuesday that you can point at. The loss arrives monthly, and every month it is both a fresh loss and the same one, so there is never a point where anyone would think to say sorry.
And if you are in treatment, the cycle manufactures hope on a timetable and removes it on a timetable. Two weeks of not knowing, then a result, then the machinery starts again. People who have not been through it hear that as trying again. It is closer to a series of small bereavements with appointments attached.
That is worth naming plainly, because a grief that repeats on a schedule and has no date on it is very hard to explain to anyone, including yourself.