My question is what am I doing that can be possibly attracting them? >>>> You are doing the right thing.
My clothes suck and most haven't even heard me speak. I've been told I'm handsome but I'm not brad Pitt.
>>>> You are in a profession that is still considered prestigious. Many lawyers want to excel, win a lot of cases, become well respected and rich... In order to do that, they put fancy clothes on, they rise their self-esteem, they work hard on their arrogance and assertiveness, they work on language skills and so on. With your clothes that suck while you being quiet, you may appear as rebel, a guy who thinks "screw all that, I'll do it my way". Girls like rebels, girls like guys who do things their own way. You are also not trying to get (chase) them like the other guys, that kind of aloofness is also attractive. You are naturally doing things that masters of seduction had to learn.
But I wouldn't dig into it too much. You are a guy and girls like guys the same way guys like girls. It is natural. The good thing is that you notice them noticing you.
If she makes a prolonged eye contact, perhaps looks you up and down while she knows that you are looking at her, I would say that it is pretty strong signal from her. She is saying: I think you are attractive, otherwise I wouldn't be looking you up and down.
If she is smiling, it probably means that she likes something or somebody while looking at you. She would be frowning if she didn't like you.
If she is asking questions she is most likely interested in hearing something from you. I would talk to her. Asking her to explain interesting law that is still not clear to you might be a good start.
As far as Brad Pitt, he is a sucker. I used to like him a lot in older movies (12 Monkeys, Seven, Fight Club,...) but I got tired of that "character" he represents. It just gets annoying after a while...