Yes, maybe it would be wise (imo) to get some distance with the traumatic event that happened, before going on the dating field so to speak. I think it would take time to process.

I am sorry though that no one was there for you (e.g. your sis) when it was a big deal.

As for being assertive, maybe let your dates know (in advance + during date, if need be) that 1) you would like to take it slow and/or 2) you are not very comfortable when people (being general, so they don't take it personally) get too close.

Could T reschedule something rather than cancel the appointment you had? I think you could do with some support.