people say they are confused when i converse

I have always had issue when in High School with public speaking, I really hated that class. Then I joined the Coast Guard were I was quite successful for 8 years. I led many teams as a senior enlisted person. I think I communicated well but I always had a little issue with voicing my opinion in groups. In 1-1 situations I was usually did pretty good. I then was in the HVAC industry where I had to interact with managers of building and did very well. I knew at this point I needed help with my writing skills but never expected to have communication issues. I then changed careers to IT and did very well. I have been doing IT for 20 years.

The problem I am having is I have been told that people are confused when I talk about a topic. It seems I skip around topic. I would like to be more assertive. I also have issues coming up with answer when prompted about personal issues.

I have landed here trying to find some answers on how I can improve my focus and ability to be more focused during discussions. I think I need to be more assertive.

Lets say for example I am trying to explain subject one and during this talk something clicks that leads me to another topic which is kind of related. But this may be way out of context.

I guess this is good enough for start.