Can trauma cause fusion?

So I know that trauma can obviously cause parts to split, but can it also cause two parts to come back together?

I experienced a traumatic event recently, and when everything settled back down and I could think again I realized that a bunch of stuff shifted around. I feel very different now, but not in the way where I feel like a new person. I feel that I'm someone I used to be. I've noticed I'm showing characteristics of two parts I previously believed were separate. I also have a lot of close memories from about seven years ago. There's about a three year period I remember very well, then it becomes very foggy and partially blank. My entire demeanor has changed. I looked at video of myself, I am not acting the same. My speech and mannerisms are different from before. They don't match up with anyone I'm recently familiar with, but I have seen very old videos with these same mannerisms.

This is very confusing. I have a few theories about what's happened. 1) A fusion of those two parts. Maybe they weren't separate seven years ago, idk. I don't know how these things work. 2) Those two parts were never separate. This option doesn't sit very well because of differences in gender expression and not identifying with either of the parts names. They also had different functions. 3) This is a completely different part that was dormant and somehow shares a lot of characteristics with the other two. 4) The obligatory "I don't have OSDDID" because I'm not officially diagnosed yet, but my therapist believes I have serious reason to be concerned. Maybe I've been shaken out of it, and this is just who I actually am.

I mostly just want to know if this kind of thing happens, if fusions can happen due to trauma. I feel better than I did before the trauma, so calm. Which I feel is maybe bizarre. If you have any experience similar to this, I'd love to hear about it.