I don't think it would be unreasonable to ask, but definitely agree to have your T present. I was given heaps of my medical records as part of an old workcover claim, and reading them was equal parts painful and unhelpful. It's a lot like my journal, with only the worst bits recorded (days where I was doing okay didn't require a lot of detail, days where I was a mess...urgh!), but worse still, it's another person's interpretation of my worst days.
Also, a lot of the language will be misunderstood. Even seemingly benign phrases like "acting out", actually have a very specific meaning and it's not the one most lay people think. So a lot of it is wide open for you to just plain misunderstand.
Also be ready not to get any info that you're actually hoping for. Details of actual conversations are rarely documented, so it's unlikely to shed a lot of light on what you may have said while dissociated. As well as the idea that things that are "important enough" to document - not exactly how it works. Some things they need to document, like if you state an intention and plan to suicide and they have to react to that. But a lot of the stuff is documented more for pure diagnostic (and medication if it's a doctor) reasons, rather than "this statement was really important to my client".
By all means, if you want to see them, ask, it's not unreasonable and there's no hurt in asking. Just be in a good place, and have your T on hand.
Personally, these days my attitude is that I don't care much what my T records for her own purposes, it's what she does with that information that concerns me.