i need a mentor to help me understand the analytics and improve my game

I think the best trainers are the unsung heroes of chess.

#18
"i) I was doing okay but then blundered because I didn't realise that my opponent had a threat
ii) I was doing okay but then blundered because I calculated some tactics wrong
iii) I was doing okay but then screwed up a drawn or winning endgame
iv) I was basically getting outplayed in the opening / middlegame even before I made blundered anything big."

Agree with i) ii) iii), but think again about iv). Being outplayed means having made a mistake. As long as you do not make any mistakes, you cannot lose a game of chess. Scrutinize the lost games you attribute to iv) and find your mistake. It may not be that obvious, but it is there for sure.

You can be the best coach for yourself because you can understand your problems better than anyone else

I have been doing the same thing since late 2018
(Didn't play much tournaments due to boards in late 2018 and 2019. I hope all Indians can understand my situation)

I found out my needs and bought books accordingly to improve and I must say that it has made a significant difference in my play(but due to that 1 year gap in 2019 I fell back to my former self)

So yeah you are the best coach you can get for yourself

#23 - you're right of course, I was oversimplfying a bit, and even in games where I'd say I'm "doing okay" it's not that I'm not making any mistakes, it's probably just that my opponent isn't playing accurately enough to capitalise on them.

My point was just that a lot of my losses are down to fairly simple mistakes and bad endgame technique, that it doesn't need a lot of deep analysis for me to work this out, and that that's quite likely to be the case for the OP too...