Hello @Twinkle. I can relate. I'm relatively senior and work in a male dominated industry, with imposter syndrome a recurring theme in my working life. On a few occasions I've been bullied and had to fight back, and this helped/forced me to develop some ways of objectively looking at my performance.
Try pulling together some hard facts about your work performance. For example, Sales made, no of client calls done, people managed, complex problems solved, gather positive quotes and feedback (however small), gather KPis (key performance indicators) for your role and measure how you are doing against them. These are only examples, find the ones relevant to your role.
Once you have these nailed, pick one or 2 per year, per quarter (or whatever cycle feels a good fit for your organisation) and create a personal mantra/ brand. Use this mantra 'casually' in conversation with your peers,and mangers regularly. For example someone asks how your team is getting on in covid , you reply 'well yes it's been tough but despite that we're doing well, for,example I achieved x (and roll out your mantra). Keep it consistent, use it often but subtly. Soon you'll hear people saying it back to you. And if they believe it, you'll start to, maybe a little anyway. 
The key is to start to use positive adjectives all the time 'I achieved' 'i delivered' , 'I devised' , 'I led' , 'i facilitated' etc etc. Women tend to use the 'we' word far too much and I think although good sometimes, can erode our own personal contribution. Over time that feeds the imposter. So start feeding the imposter with the good stuff you have achieved.
I hope this helps.