Is my stuttering purely psychological?

Is my stuttering purely psychological? Hi, I've been struggling with my stutter since I was 6-7 years old (I'm 25 now) and I was wondering if my problem is psychological, neurological or just a habit that I developed (because my dad stutters as well) and I just got used to it. My stutter is not on a terrible level, I can usually have a normal conversation and just stutter 3 or 4 times after a 5 minute conversation but there are times that it completely ruins my social interactions because I'm afraid to start a conversation because I can feel that I will stutter on my next sentence, so I decide to stay silent. I went to a therapist for other reasons and he insisted that I go to logotherapy because he believes that my stutter is based on years of habit of talking that way. However I disagreed with him for a couple of reasons: 1) Why do I only stutter A LOT when talking to family members ? I mean I stutter on 8 out 10 words each and every time. I can have the same conversation with a stranger without stuttering on a single word but I stutter most of the words when talking to a family member or sometimes a close friend. (I don't feel any kind of fear towards them) 2) When I'm ready to make a phone call, I'm repeating the first sentence that I will say out loud 4-5 times before he/she picks up and I can say that with no problem at all, but once they pick up I try to repeat the same sentence but I stutter on the first words. Aside from myself I have seen other people stutter a lot and that's why for the past few months I've been actively researching about the topic and I try to observe at the time each person stutters with a hope to find a common connection and maybe a solution. I know that science hasn't officially discovered the real cause of stuttering but what do you guys believe? Is it psychological or neurological or something else? It's sad that some people have so much to say but decide to stay silent because of their fear of stuttering.