- He helped her to lift the box.
We often use the infinitive without to. This is rather informal.
- He helped her lift the box.
If you say that you can’t help doing something, you mean that you can’t stop yourself doing it.
- Sorry I broke the cup – I couldn’t help it.
- I can’t help wondering what I should do next.
Can’t help can be followed by but + infinitive without to. The meaning is the same as can’t help — ing. This structure is common in American English.
- I can’t help but wonder what I should do next.