I see. I understand that you are talking about a traumatic experience that happened to you when you were 13, a form of abuse, possibly sexual abuse. Children at that age trust adults and depend on them to protect them. In this case, your uncle violated your trust and your mum, as you mentioned, failed to protect you. Therefore, it is very normal for a child with similar experiences to develop mistrust to adults and men, especially if these traumatic events are not resolved or addressed properly. Children at this age with these sort of experiences can develop negative self image, feelings of guilt and shame and feelings of mistrust and helplessness. These feelings often continue into adulthood and cause the person suffering until the person seeks therapy.
I do not know your partner and therefore the quality of the relationship and his purpose of telling you this. However, it is very likely that he has a point. It would be very understandable if you had developed these personality traits (mistrust, being introvert, negative outlook). As you do not seem to dispute them, I guess you agree on a level with him. If this is the case, that would indicate that you are in need of psychotherapy. Approaching us now, also indicates that you feel that you are still affected by this experience and that it is time for you to deal with it.
I would definitely encourage you to speak to your GP about your need to engage in therapy or counseling. Depending on your current psychological/ emotional condition e.g. mood and general functioning, he could refer you to either your local mental health team or to a near by counseling service. These are funded by NHS.
You did the right thing contacting us. However, you need to address what happened to you back then and find a way to move forward. It is very hard to overcome physical or sexual abuse by yourself and you would need the help of a professional. Therapy would give you the chance to look deeper into the issues around the abuse and your feelings and thoughts about it and the people involved. even though it may seem to you as "old news" you can probably still see how this incident affects you to date. Therefore, do not dismiss your feelings. You can only do this for yourself.
I hope this helps
All the best to you