the red marks seem like pimples. I think they developed because of my hair being so sweaty from riding bicycle
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You don't get red marks from your hair being sweaty. It might be exercised induced reaction though. If it concerns you, have a doctor check it out.
As far as days off, take at least one a week. Doing 10-15 miles a day eventy day won't help you improve after you get to a certain point. Alternate fast/easy or long/short. You can switch a day off for an easy or short day.