There are several which I think do scrape into being Crit. A, but all are on the mild end of their spectrums - some non-violent, non-penetrative childhood sexual abuse, something that nowadays might be called grooming, another bewildering sexual assault in a very public place, one particular incident of abuse that could only happen because my mother insisted on me sharing a bed with someone inappropriate, something that might be rape or might be an error.
Yes, what
@Cashew said. There's no 'lesser' or 'greater' scale on criterion A trauma. If I remove your conditional language, you experienced childhood sexual abuse, sexual assault, and rape. You also had a child who was stillborn. In your description of that event, I can see how the entire medical situation you went through was really screwed up - but I think the trauma you endured was in giving birth to your dead child. It does not sound like you had time to prepare for that, and so it was unexpected death of someone close to you, that you witnessed. (in Crit. A terms).
We dissociate to greater or lesser degrees, in the moment, to cope. Then, when similar stressors pile up or triggers occur, we can dissociate again.
I've been dissociated. I've never lost time consistently. For me, dissociation is appropriately 'filed' as a symptom of my PTSD, not as a separate disorder. It isn't especially larger than my other PTSD symptoms.
If I'm understanding you correctly, you are finding that your therapist is pushing some kind of theory of dissociation at you, and you don't think it fits your symptoms.
But given everything you've outlined, you more than certainly meet the criteria for PTSD - so if you are symptomatic for PTSD, and you've been diagnosed for it, that diagnosis is likely accurate. You may dissociate as a symptom of PTSD.
Nothing with mental illness is an either-or, black and white situation. It's not a blood test. All symptoms scale from mild to severe, and disorders overlap. What seems more important is that your therapist is perhaps not listening to you, and instead pushing an agenda at you.
(By the way, structural dissociation is nothing more or less than a way of thinking about dissociation - it's a theory, a set of ideas, not a fact unto itself. So it's useful if the language used rings true for you - and if that language doesn't sound like what you experience, then it's just not useful, plain and simple.)