Im having trouble asking a girl out

So im pretty into this girl that I know, she's friends with my best buds sister and his sister has been trying to set us up from the start from when we met. Which was about 3 months ago. Man putting it into words really shows how slow I am at this but atleast im trying again. Seriously though I've always had an issue with making the shot, it feels like im about to jump into cold water and the whole, should I or should I not? comes into play. Its just fear of rejection, I know, and I've been told that this girl likes me but that was a while ago and im afraid that its been too long and that because I was too slow I cant ask her out now.
I say this because I tend to go over my buddies house to hang out with a group of friends I got, and her and my friends sisters are usually there playing a game of cards with some friends and family. Instead of going downstairs to hang out, I decided to sit down and play the game so I can actually be around her more and spark a conversation. But damn i dont know if its because im nervous or she's shy because I have a hard time talking to this girl. Usually a conversation with her is short and has ALOT of tension. I try and spark something then its just me talking then she looks around and avoids the conversation entirely. They've told me that this girl is into me, but in all honesty it dont feel the same anymore. Like when I first met her it was easy to notice that she was into me but now, it feels dragged out. While there I also felt like a loser for some weird reason. I had not reason actually, I just felt that way and it broke me until I couldn't make my move or even engage. I have some serious confidence issues that I really need to work on, my therapist told me that I lack confidence in myself and I really haven't noticed it until I was told that. Like if you look at me first hand I'm a pretty good looking guy and I work out a lot so I have a nice body too. But on the inside im just a soft little baby that hurts himself with words. I guess ill just move on and focus on me some more and learn to get confident before I jump into a relationship, because I noticed that I keep thinking how having one will fix me, and that's the last thing I want to do.

I'm talking about this because I noticed that I am garbage at this relationship thing, porn has really made harder for me for sure, and crippled a lot of my confidence because I have extreme fetishes like trans porn. Stepping into the real world and seeing my position in it hurts like hell. Like I know people who are grandmasters at this sort of stuff, and would know the next best thing to do in my position, but I dont know. I have zero clue on how to do any of this, and I feel like a 14 year old kid trying his best to get 20 year old girls if that makes sense. Seriously though I blame myself and porn for what its done to me, and now I can actually see the difference of a porn fetish and a real connection, their almost entirely different if not completely. It was hard for me to differentiate the two before but now its like night and day.
A lot of my mental alarms went off for a while but Im trying to remind myself that these feelings are ok and only expose what I really feel, it feels like shit but I got to teach my brain that ill be ok and that im not that scared 12 year old anymore and that im a 20 year old man now, and I cant be scared of these things anymore.

Im not asking for advice on how to ask her out, because its as simple as just doing it, im just ranting on a forum to kind of get things out of my system, I feel it to be helpful especially when im feeling down.