I hope that this message massaged your ego to a satisfactory degree.
I'm pretty bad about defaulting to masculine pronouns myself, and this simple exchange has done a lot to motivate me to break that habit (I would have also assumed your gender to be male, and would not have really thought about that assumption if not for this comment). Conversely, I think that would have just glazed over an angry/offended response, since I think it's clear that the person you're replying to meant no offense. So, thanks!
More on-topic (in response to your GP comment): I have a pretty similar family background, and have also experienced a lot of self-doubt. I think a lot of us (people in tech) suffer from impostor syndrome at times; the approach that helped me to overcome it is "fake it 'til you make it", especially in your internal dialogue. Try your best to project confidence in your abilities, and (more importantly) squash that little voice in your head that says you're not good enough whenever you hear it - even if you're inclined to agree with it.
I know this is easier said than done, but I think that it really helps improve the situation. For example, say you disagree with something said in a meeting:
<self-doubting inner voice>: "Keep your mouth shut, you're just going to look stupid!"
<self-affirming inner voice>: "No! I may not know everything about this subject, but I know a lot, and they haven't considered X!"
<out-loud>: "I'm not an expert on this topic, but it seems to me that we might be overlooking X...<make your argument>...Does that make sense, or am I missing something?"
As long as you're careful not to come off as hostile (note that the "out-loud" part has a deliberately humble tone and invites further discussion if others disagree), the worst-case scenario is you get some free education from someone more experienced than you; best-case, you get some immediate, external validation that you do know what you're doing. In either case, you're working towards breaking the habit of self doubt.
Anecdotally, I helped a friend get his first job in tech a couple of years back (he was previously a trash hauler), working as my assistant (I'm a DevOp) because I knew he'd be great at it if given the chance. His impostor syndrome caused him to totally choke in the final interview (upper management actively didn't want to hire him, but I managed to convince them that he'd be worth the low salary he was willing to take). It took him over a year to begin to believe that he wasn't an impostor, rather just new to the field. He worked hard, and followed my advice above, and his confidence gradually improved. Today, he's the Senior DevOps Engineer at that company (my old job), leading a team of 6, and making twice as much money as when he started. If he decides he wants to move to a "top" company at this point, he should have no problem.
I guess my point is that impostor syndrome really sucks, but if you actively work at it, it gets better.
Also, based on your comments on this thread, you seem pretty cool to me. If you're interested, shoot me an email (in my profile), and I'll gladly help you get an interview at my current company (Cloudera).
I'm going to try putting some of your suggestions into practice. I'm at a crossroads in my career, having recently been separated from my job due to budget cuts. Even though my job loss wasn't an indictment of my worth as a person or the craftsmanship of my work, my confidence still took a significant blow.
Staying motivated while looking, applying, and interviewing for jobs you believe you don't deserve to get is challenging, to say the least.