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Let me paint a picture of my background in brief. I did my undergraduate degree in mechanical engineering. I was a good student (almost all A's) till my high school. However, I struggled a lot in my first two years of engineering. I failed 3 subjects and had to retake them. I did fairly well in my last two years and managed a GPA of 3.7. But, my early failure played a heavy toll on my self confidence. I always felt and still feel like I am not worthy for my grades or getting a job.
I was interested in research, so went to a better school for master's degree. Again, though I had very good grades there, I struggled a lot during my job interviews. I always felt inadequate and unconfident about my ability to sustain in that job. As a result I did not get selected in those companies. I got offer in a small company which hired me only looking at my grades. My professors also said that I deserve better workplace but I didn't get it only because of my lack of self confidence and technical speaking skills.
I figured that, since I loved doing research, I should go for a PhD. I worked hard during the last five years. I tried coming out of my comfort zone, try different things, work on challenging projects. I started feeling confident midway through my PhD. However, now I am in my last year and towards the end of writing my thesis. And I am feeling the same anxiety of technical inadequacy and unworthiness.
I am again getting the feeling that I am upto no good and I can't get a decent job or postdoc position with my skillset. Only issue is that I am 29 years old and I will have to get a proper job soon to support my family. I don't know if I am capable of doing that.
My question is, assuming that I suffer from severe case of imposter syndrome, what's my remedy? How can I improve my confidence levels during an interview? I want to feel alive during job search and interviews. I don't want to feel all hopeless and inadequate during any future opportunities.
Are there any suggestions?