I think you are just unlucky with your draws. Again, this is gambling and any outcome is possible given the circumstances of what you are betting. If you have noticed this kind of pattern on your bets, then why continue to bet huge amounts in the first place? In addition, if you suspect that an online casino is allegedly "cheating", then post all the necessary proof to substantiate your claim.
Lastly, I also want to point out that any issues with a certain gambling website should be fixed by simply switching to another online casino. There are lots of online casinos available and some offer better bonuses/rewards as compared to the others.