Imposter Syndrome is extremely common in tech. We are constantly learning and growing our skills. So much so, that we can forget how far we've come.
The only ways I have found to combat this is to keep a running list of accomplishments and to surround myself with people I trust. The accomplishments list helps me to see how much I have learned. I trust my tech friends to be truthful about my skills when I ask. Together, these keep most of the ugliness of imposter syndrome away.
Last weekend, I was questioning my skills again. All it took was a colleague who I looked up to saying "Oh! I really like that timeline and those skill bars. How did you do that?" on my new website to make me remember I do belong and know my stuff.
Make a list, find trusted colleagues/friends, and remember you belong.