Opening up

Trigger warning!....
Hi ims. I just wanna get something off my chest... I have never, and I mean never spoken about real emotions like when I'm really sad or really in pain (even physical, unless I can't help it but even then I make out im still fine) to anyone. And I've recently started therapy sessions because of my anxiety and he's slowly tapping into some deeper emotions which I don't mean to resist, I want to tel him these things, but I sometimes don't remember because it's blocked.
He asked me how long I've been harming myself and I blurted out since high school (12 years ago) that shocked me that I said that and besides bringing up horrible thoughts, I felt like it unlocked something a little bit. I do want to delve deeper with him because I feel there's a whole person that not one single person knows exist. Like I used to be bulimic and tried to harm myself regularly - I was really depressed (undiagnosed of course). It's hard to remember details sometimes because I've suppressed everything and so many areas of my life are blocked off. I'm really liking talking to my therapist, I feel really safe, I just wish the sessions went longer than an hour.
Oh and I guess it's also hard opening up because I've never done it before and it sounds really stupid when I go to say things out loud. But hopefully one day I'd be comfortable opening up to a loved one.