Serious brain fog. Guesses at it,

I'm having problems with concentration, focus and motivation lately. I was depressed for some time, but I think I've started to feel better but now I'm having some serious brain fog. I'm a IInd Sem Engineering student and I can't remember the last time I could focus and understand something in class. This problem has been there since high school, the inattentiveness in class but now it's really affecting my grades and I want to figure out a way to deal with it. I think I might have ADD. I'm pretty sure about it but it could be that I'm just making wild uninformed guesses at it, thanks to google. I've been wanting to get myself checked by a psychologist and probably try some stimulants (adderall or something) but as I said I just have lost ALL the motivation to even go out. I wanted to know how does it normally go after I visit to a psych, what is the procedure normally followed and what happens if I'm detected with ADD?