(19 m, kissless virgin for context)

So, I haven't been able to pass a certain point with girls. I simply don't know how to, or just won't, make a move. Even if she wants it or is being obvious, I just can't escalate.

For illustration, I'll give a quick recap of my night yesterday. A girl hit me up asking if I wanted to hang out (she has a boyfriend, but I'm nearly certain she's still interested in me). I said sure and that I'd see her once I got back from the gym. We meet up in her dorm room, catch up for a bit and then decide to smoke pot. We then go to my room to grab the stuff, say hi to my friends, and leave. We walk to an abandoned church nearby, light up, play music, and talk. After a bit, we decide to go back to her room.

Now all this time, I've been making her laugh, leading well, and giving light kino. We had a running joke about her turning into an old lady. I'd say I was doing well, but the weed was exacerbating my self-consciousness, and I started second guessing myself.

So we hung out at her place for a while. Her roommate (who has a crush on me) was in the other room watching a movie. Eventually we turn on a movie too. I was with her, alone, in the dark, right next to each other for like 2 hours until like 2:30 am and I didn't do a damn thing. No arm over her shoulder, no cuddling, no kiss, she even put her legs on mine and I didn't keep them there.

I've dropped the ball like this all the time with girls, and several times before with this particular girl. I just can't pull the trigger and try to get physical. Maybe it's a self esteem thing, or I'm afraid of intimacy; I don't know. I just want to stop it. I've never kissed a girl before, it seems alien to me and I have no conception of how to kiss people. Even my parents.

Help me out lads, I've got no clue how to progress.