Hi Pelin!
Depending on your context, you can use both.
Check out the example.
Your friend or special someone:
“I like you a lot, that’s the reason why i travelled all the way here to see how you’re doing.
You should know me better by now.”
You boss:
“I have a specific requirement for this job.
You should've known me better by now. I don’t like this outcome!!
Have a great one!