I could regain you could regain he could regain we could regain you could regain they could regain
V-ing form
I could be regaining you could be regaining he could be regaining we could be regaining you could be regaining they could be regaining
Perfect
I could have regained you could have regained he could have regained we could have regained you could have regained they could have regained
V-ing perfect
I could have been regaining you could have been regaining he could have been regaining we could have been regaining you could have been regaining they could have been regaining
Negation
Simple form
I couldn't regain you couldn't regain he couldn't regain we couldn't regain you couldn't regain they couldn't regain
V-ing form
I couldn't be regaining you couldn't be regaining he couldn't be regaining we couldn't be regaining you couldn't be regaining they couldn't be regaining
Perfect
I couldn't have regained you couldn't have regained he couldn't have regained we couldn't have regained you couldn't have regained they couldn't have regained
V-ing perfect
I couldn't have been regaining you couldn't have been regaining he couldn't have been regaining we couldn't have been regaining you couldn't have been regaining they couldn't have been regaining
Interrogative form
Simple form
could I regain? could you regain? could he regain? could we regain? could you regain? could they regain?
V-ing form
could I be regaining? could you be regaining? could he be regaining? could we be regaining? could you be regaining? could they be regaining?
Perfect
could I have regained? could you have regained? could he have regained? could we have regained? could you have regained? could they have regained?
V-ing perfect
could I have been regaining? could you have been regaining? could he have been regaining? could we have been regaining? could you have been regaining? could they have been regaining?
Interro-negative form
Simple form
couldn't I regain? couldn't you regain? couldn't he regain? couldn't we regain? couldn't you regain? couldn't they regain?
V-ing form
couldn't I be regaining? couldn't you be regaining? couldn't he be regaining? couldn't we be regaining? couldn't you be regaining? couldn't they be regaining?
Perfect
couldn't I have regained? couldn't you have regained? couldn't he have regained? couldn't we have regained? couldn't you have regained? couldn't they have regained?
V-ing perfect
couldn't I have been regaining? couldn't you have been regaining? couldn't he have been regaining? couldn't we have been regaining? couldn't you have been regaining? couldn't they have been regaining?