What are the reasons some one may feel constantly depressed in their relationship?

what are the reasons or causes for feeling depressed, constantly on edge or hurt in a relationship? even if your partner tries to do everything they can to make you happy and safe.
Lately I’ve been feeling constantly on edge, worried, insecure, depressed and I have no idea why… I feel like I’m also not trusting him 100% ... He has done a couple of things to hurt me (such as my previous questions) but I love him and breaking up is no option… I’m just wondering am I not letting go or what can I do to not feel this way.