Hello,
I have a few questions regarding grammar. If possible, please do not offer a revision or an alternative way to say the sentences.

a.) You could've just said you hated me.
b.) You could've just said you hate me.
The sentence should say that the recipient
still hates the speaker.
Would the second sentence be incorrect? I am wondering if using "hated" would mean the recipient no longer does, or is it the appropriate one because of parallelism (could've + said + hated)? Would the above mean:
a.) The recipient no longer hates the person thus "hated".
b.) The recipient still hates the person thus "hate".
Also, is the ommission of "I" acceptable in the following sentences?
a.) I just called the doctor. (Just called the doctor.)
b.) I just ate lunch. (Just ate lunch.)
c.) I've just taken a bath. (Just taken a bath.)
I usually encounter the first and second sentecnces. Should the third say "Just took a bath?"
Thank you very much.