Talk to General Physician on Not Ability To Maintain Attention

hi, i am 22 year student, I can't maintain attention while doing anything. If i try to study i would be doing good for a few minutes until i find myself lost in thoughts, i would read whole page and when about to reach end i would notice that i haven't understood anything as i was lost in thoughts and just reading not understanding, when i am in group with people, i cant remain focused on topic my mind just wonders away, When talking to people i have tendency to say things that shouldn't be said, as i am not paying attention to them at all, one last thing i am mostly during day lost in thoughts my mind would reach negetive thoughts and ultimately ruin my mood. anything that can be wrong?