Not enough context to say. And really, my opinion one way or another is (and should be) worthless. If you feel used, your perception here is necessarily valid regardless of how grounded in reality.

The key here is to examine your own interpersonal template and remedy whatever it is that results in these relationship dynamics in which you keep finding yourself. If you weren't actually in an exploitative relationship, it's up to you to address the thought patterns that led you to believe that. If the relationship was exploitative, then it's up to you to address your traumas and lack of boundaries that precipitate these relationships.

I'll close with: all relationships are transactional in one way or another. The exchange might not always be immediately apparent, yet can be utterly benign and mutually beneficial. Just because someone wants something from you doesn't mean it's nefarious. You need to define your boundaries and needs, then be explicit about that with potential partners.

Its ok to feel angry. It doesn't even have to be justified. You don't have to take out your anger on people, you can just feel it. It is a part of the grieving process.