Okay, the thing is I have written a topic about it,
But I think I need to write a bit longer thing about that.
So, my ex, when we first met, after few days in the relationship learnt my codes on my phone. (you know the screen code)
And he was using my phone during the night, and then in the morning said (I simply was “updating your programmes”)
The scariest thing, which I believe he said ~three months ago was
“I can hack your PC with one flash, within few seconds” (Hmm I thought, and how do you know how you smart guy :)) )
overall, he was really not open to me, we’ve been almost two years together but he never wanted to open about his past, he never showed his emotions etc.
Few times he even mentioned, that some guys spy their wives with cameras, “to know what they’re doing”
and I felt like… I suddenly became paranoid. IDK, am I simply paranoid because of that, because actually he never did anything bad for me. No physical, emotional abuse, just simply was often cold and distant, and of course these strange things.
In previous relationships no one said “I can hack your PC” and never tried to use my phone without my permission.
And yes, on my facebook I’ve always found logins which were called not “iphone” (which is mine) But simply (WHAT THE HELL) “PHONE” actually, phone, nothing else. IP adress was sometimes mine, but it is easy to change I belive.
SO long story short, should I be concerned or am I paranoid ?
because, in my past, during psychosis, I WAS PARANOID ABOUT EVERYONE.
And simple things, like smile could seem to me like “I will do something bad to you”
And actually, I was always paranoid of my boyfriends.
Somehow, I am stable now, and somewhere deeply I believe this particular case is a bit different.
Are you sure he was just not joking or trying to scare you?
I remember when I was a teen I was a daily member of a chatroom I was shy about my location like here, and some guy said that he could see our ‘‘ip adress and know where we live’’ he never did crap.
IDK.
i know that when he was teen, he was very much into PC stuff, but I truly don’t know if he can hack.
Later he only said “You know I wouldn’t do that.” And smiled
That’s why I feel like I am simply being paranoid.
But actually, I felt about him strange from the very beginning.
Because when we started our relationship he showed me few my very likable songs (which I was posting on FB), actually they are popular but…(Even then I felt paranoid because I felt whoah)
once he said he knew me from FB long time ago, because I was his friend’s friend. (yep, super strange is that he remembered me from these pictures, he never saw me in reality)
And he asked my brother to get to know me. (my brother was also his friend)
overall, it seemed like he wanted to know me long time ago, and these things like super early learning my phone screen pass, hacking pc, facebook…
Maybe it’s simply strange. Maybe I am paranoid.
Saddest is during pscyhosis even few words could create paranoia in me. Even till this day, when my doctor says “You’re stable” I feel I am not.
Sometimes he just knew what I am thinking. Not talking about thought broadcasting… but like he known more than I said. 
meh Idk…
I did that kind of stuff saying I was a computer pro but I can’t even code that well. Did you have psychosis in your teens? Because that would be a pretty crappy thing to say to you if he knew about your condition.
I’m sorry you are feeling this way, I totally get that.
If you’re concerned, then change all your passwords?
yup, in my teens,
He knows what happened in my past,
but even as he said " I don’t read about such things" (like your illness)
Thanks for support. <3 Actually, sometimes I think I so craved for him to love me (because often I simply felt unloved) that I somehow fall into this delusional thinking. But actually like I said, IDK why I still feel paranoid sometimes. Maybe this thing will stay forever with me.,
I tried it like… for four-five times.
Still, sometimes I see strange logins into fb.
Sometimes Facebook is just weird about what it reports your device as.
I noticed that!
yup now I more and more believe I felt into paranoia trap. 
well, still, the thing he was using my phone without my permission
is a very huge red flag 