If you play online poker on big, trusted sites. You are ABSOLUTELY NOT being scammed, cheated etc. You probably won't like my answer. If you give up poker for good, that is fine. It is not for everybody. If you ever come back. Please read my answer.
There are two potential groups that can scam you. 1) the client/site itself, or 2) the people that play on the client independent from the client itself.
1) if you play on big sites you can trust the site completely. They have a reputation to keep up. They already make a hundred times more money on rake than they would by letting their bots play. Or whatever else you can think off. Reputation is everything. It would make no sense to risk it all, for a little bit extra cash.
2) there will always be people who try to get an unfair advantage if money is involved. Through colliding, scamming, writing bots, exploiting bugs in the software. And to be fair, everything can be exploited in theory. But in practice the big sites/clients will try their absolute best to continually improve their software to counter these people. Bots and colliding players are easily spotted and banned. Again reputation is everything. I doubt it, but maybe you will come across a bot or colliding players once or twice in your life. However, it will happen very very rarely.
Poker sites also don't rig the site for bad or good players. It is all fair.
Online poker is just as fair as live poker. You are just as likely to come across colliding players live.
Study hard. Review hands. Buy software to improve and to track your results. By tracking your results you can more easily figure out whether you are truly unlucky, or just playing bad. Have a great mindset. Poker is not an easy game. If you don't try your absolute best, why would you win against players who do?