Re: I might have ADD?
The 'lost in your own mind' symptoms certainly could be the inattentive subtype of ADHD. I would recommend consulting with a professional that specializes in ADHD for a diagnosis. Attention problems can be caused by a myriad of issues, both mental/emotional such as depression, PTSD, FASD, brain damage, etc. as well as physical problems like thyroid disorders.
Depression can result from a number of causes, again both mental/emotional and physical. Depression can also lead to attention problems that can be mistaken for ADHD.