Does much crying affect brain?

Not at all: I expect you don't mean actual organic brain damage but emotional health. And the answer to that is less absolute. However, I'd still say - don't worry about it. More important may be your reasons for frequent/lengthy/intense crying. Talk w/ a person you respect and trust about the sadness. If there's no cause you know, have a psych eval and/or see a doctor for help. Crying can be helpful.