I find it really hard to process this relationship, everything that went on and how and why it ended. I feel like I can no longer trust my mind, and I had lost myself. My mental was getting played around like a puppet.

It sounds to me like you were just ignoring some pretty blatant red flags that should be, in the future, seen as complete dealbreakers.

 6 months into our relationship, I discovered the first lie. He was sexting with some random girl from IG, and that girl reported it to me with screenshot, etc

This guy was sexting another girl, which this girl proved with a screenshot, and then lied to you about it. That is a dealbreaker. Dump any guy that does this and do NOT look back.

A few weeks later I found out he actually has a son from his past relationship, a kid who he never disclosed when we first started going out, he doesnt talk to him anymore because his ex before me asked him to choose between her or the kid and he chose her.

First this guy doesn’t tell you he has a child after 6 MONTHS of dating, and then you find out that he chose a woman over his own child. This is a huge, HUGE character flaw. It screams “lack of integrity” and “lack of responsibility.” Again, not great characteristics to have in a significant other.

He’s lied to you over and over and your gut instinct was screaming at you that something was off, because it was. All of the things he told you make no difference because he was only saying those things to take the blame off of him and put it squarely on you because he very, very clearly does not take responsibility for anything.  It may have FELT like a good relationship because you are ready for a good relationship and you were hoping that was it, so you ignored some very clear signs of dysfunction.  Next time, just pay attention to those signs.

There is nothing wrong with you beyond the fact that you chose to ignore those red flags and allowed him to place blame on you instead of dumping him right then and there. Next time, just dump the jerk and keep dumping the jerks until you finally find yourself a good one with no dealbreaking red flags.