Can Four Concussions Alter Brain Activity Level? Have Trouble Sleeping, Low Self-esteem

Hello, My name is Max Berntsson and I have been living a pretty wild life with mountain climbing and skateboarding, through these sports I have caused some minor concussions. I guess my question to you is really stupid but I have nothing to lose by asking. After four concussions made from falling, can it be that my brain doesn t work at the same level as it used to? Have I become stupid? I have had som struggles lately in my life and it isn t just because of my injuries but some are. I have trouble sleeping and waking up and my self-esteem is worse not only that but my life spirit isn t what it used to be, I have become depressed and I never imagined myself being so. Sometimes it feels like my head is pumping blood and it s really unnatural so to say. I been to the doctor and scanned my head and they didn t see anything, I have had one more injury sense then but not as severe. I m soon starting college and it feels like my memory isn t what it used to be, this makes me especially worried. I m trying to be as frank as I can be but there is limits to my knowledge in this subject and I really appreciated if you write me back. Best regards Max Berntsson