I couldn't help but 后面是跟to do还是do?

can't help but 后面加to do 还是do? can't help but do还是can't help but to do can't help but do 和couldn't help but do 只是时态的区别吗? I couldn't help but cry.为什么后面不用不定式to cry呢? couldn't help but do 什么意思啊 i couldn't help but could not but后面是do还是to do来着 can't help but to do we can do nothing but是跟to do 还是跟do啊~ I cannot help but to do sth I want to help her but I don't know what I can do to her Promise后面跟to do还是doing?