Forgiving yourself past

I regret not doing and caring of family when i was a kid and now only 1 person left, um 19 and i cant stop thinking about this stuff everyday is it gonna Get worse ? tomorrow ill try to scedule a head doctor but wanted a oppinion from someone who know better than me i have Been thinking a lot about a tope the only thing stopping me now is my dad wich also hás terminal câncer after hes gone idk How I Will be able to keep living