"Woken up" always jars my ear. I'd say, "I just woke up" or "I've just awakened."

This is one area where American and British English differ. If you have studied British English, you probably learnt that 'just','yet' and 'already' take a present perfect tense. However, American English tends to use the past simple with these words. So, the answer is : either one can be correct, depending on the variety of English you are using.