I’m not sure you’re thinking of this in the most helpful way. A lot of times we are attracted to the kind of people that make us feel comfortable, and what makes us feel comfortable is what we have experience with. So for example if we have a toxic relationship with our parents, or with a first relationship, often we become attracted to people who embody similar toxicity. So its likely not that you are unattractive, but instead need to rethink why you have been attracted to the people who cheated on you. Maybe they all have attributes in common? Anyway, being cheated on sucks, and I’m sorry you have to deal with that.