I have got to agree with Dennis, a fuzzy - even 3 a week - while likely better than what a pet store is giving him, is still far to small. Do you have a scale? A general rule of thumb is a prey item that is 10-15% of your snake's body weight. If weighing isn't currently an option that's okay, you can also offer a prey item that is approximately the same circumference as the widest part of the snake. Granted if he is under fed that still leaves you slowly working up to the type of prey he should be on but he'll start beefing up in no time. To give you some idea, if he is 8 months old, I have a 6 month old that is happily - and easily - slurping down weaned rats every 5 days.
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