It sounds like you need the help of a professional and have needed that help for quite some time. Depression can be successfully treated. CTE does not change that. Self-harm is a serious issue needing attention.

Nothing suggests boxers have a slower onset of CTE. It has had a different name for decades, dementia pugilistica. Since boxers win because they can better tolerate blows to the head, it may be that they (successful boxers) have brains with greater tolerance, to a point.

So, find a good doctor. I personally think a psychiatrist with experience with brain trauma would be best. A neuro rehab hospital is often a good source for a referral. They may even have a good psychiatrist on staff. In some cases, a neuro-psychologist can fill the need but they may need to refer to a MD for meds.

Considering the symptoms you are experiencing, the side-effects of an SSRI or SNRI med would be worth the benefits of a stabilized mind.

Your county mental health department may also be able to help.

So, please, get some professional help.