I've had an online relationship, and trust me, it was awful. You become emotionally attached to someone you don't even know or have never seen, and that is not present for you. And then things happen, and we get separated. And it hurts, just like any other kind of relationship. But the chances for not working out are much bigger than any normal relationship. So, what you are going on is completely normal. It is super ok to have these doubdts. Trust me, you are fine. There is nothing wrong with you.
And you will get over this. But if you would like an advice, just don't use online dating anymore