I have a super beginner’s book (because I am a beginner 
) with sentences like these:
Stēllās spectāre amō. I love to watch the stars.
Natāre possum. I am able to swim.
Assuming that the above sentences are ok, are the following sentences possible grammatical forms?
Present infinitive with perfect verb:
Stēllās spectāre amāvī. I (have) loved to watch the stars.
Natāre potuī. I was able to swim./I have been able to swim.
Present infinitive with imperfect verb:
Stēllās spectāre amābam. I used to love to watch the stars./I was loving to watch the stars?
Natāre poteram. I used to be able to swim./ I was being able to swim
I know the sentences in italics are odd in English but am trying to capture a possible meaning sense.
I am studying on my own so any help is really appreciated.