Girlfriend gets into Combative Contradicting phases that drives me crazy

GIRLFRIEND GETS INTO COMBATIVE CONTRADICTING PHASES THAT DRIVES ME CRAZY

I feel my friend has two different modes. Insanely awesome and sweet and the girl I want to marry is funny, supportive and affectionate. But then she will get into these phase of being combative.

Constantly cutting me down, contradicting everything I say. Someday I could say it’s raining outside and she will find a reason to say “no actually” Lol..!
This has happened a dozen times and a day I start to get angry, frustrated and exhausted until I just snap. “Why is everything I say wrong to you?” seems she is actually trying to find faults in everything I do or say even when I’m being nice or just sharing a simple opinion; it makes me feel so stupid.

Everything is just “no” it hurts my feelings and I had to resort to being quiet around her because I can’t take it anymore.
We have argued about this over and over again (though not always an argument). The last time this happened I made her understand that the way she cuts me down really hurts me a lot and it makes me think of breaking up with her. She readjusted for a short while; things were moving on better compared to before.

I know it may sound insensitive, but that period was one of the best periods of my life
because we got along so well and bonded so much more.
Things continued to be this great until 2 months ago. This time, is worse than ever. I can’t do anything without being contradicted or told how wrong I am. I could either fight back which leads to more bickering back and forth. (We argued like 7 times yesterday alone and I’m fed up) or should I be quiet and suck it in and hold in all my frustrations? Sometimes she will contradict me over something she once
said not even or agreed with initially.
I had to keep reminding her to stop being so rude to me and argumentative. Could it be she have no self-awareness when she’s doing it because she always acts surprised when I bring it up? What should I do entirely because I do not want to throw a relationship of 8 years just like that.