Has my brother experienced a breakdown of some sort?

My brother 24 has broken up with his girlfriend as she kept telling him how much of a waster he was , how he cant read , has no job , doesnt etc ... he has always had low self esteem and tought of himself as being stupid and below everyone else . but to cut to the point last week the had a fight and he stormed out and we found him and he was acting really strange , louder and agressive . he told us he took 17 relaxing tablets that he was not perscribed ! 3 days on and he is still acting very odd like louder than usual and forget full and repeating himself alot ..not agressive anymore talking about how he wants to turn his life around ... but he is not the same person ... this may sound so confusing but im very worried about him and he doesnt want to see a doc . if anyone could help that would be great ....... ps he has smoked alot of cannabis in the last few weeks