You should be concerned you're messing up your sleep. You need regular habits and you should go to bed earlier. Your weekend sleep says you're trying to "catch up" from the shortchange of the week and not even succeeding doing that.

The only way you can know how many hours sleep you need is to consistently, on a week you don't have school/anything to do, go to bed at 10:00 or 11:00 every night for the week and see when you naturally wake the next morning. The first part of the week you'll probably be a mess from your previous week's deficit but toward the end of the week I bet you're waking at 8:00-10:00 the next morning, refreshed and feeling much better.

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