When i started playing the game today and when I won it said 3 matches to yellow belt. That was 15 matches ago. Any reason why this is happening and if so how do you fix it?

If you do easy fights like if you win on the frame 1 the match dont work or if you are farming whit the same Tori or Internet.

how come i have this problem and im blue and im in public and semipro lobbys?

100 games a day. Once you accede that it doesn't give you anymore qi until the next day.