I am a physically healthy 17 year old, in my first year of sixth form.
I have a healthy diet, and have always been very health-conscious.
However, recently, I have had a problem. I can't keep attention for long, no matter how hard I try. It happens in all aspects, including class and just regular social activities.

I'll be listening in class and then suddenly my mind will rail off into thinking of all sorts of things, such as the universe, religion, or just any vivid and deep thought. I try my best to keep attention but I always trail off, and it affects my ability to work greatly.

In social situations, I can be talking to someone about something, and then suddenly I'll start thinking of something else, and it makes a lot of conversations slow, and I have to keep stopping and starting, or say something like "Wait a minute, let me think..." to get back on track.

Is this ADD/ADHD?

Thank you, if you took the time to read this.