Firstly - the penance we are given in the confessional isn’t meant to be complete satisfaction for our sins. As if a priest could ever accurately measure which prayers or which amount of prayers would constitute complete satisfaction anyway. It IS meant to be a partial satisfaction, and is meant to encourage us to resume the prayer life that has been damaged by our sins. And we are meant of our own volition to pray regularly and do other penitential acts as well.
That’s why, for example, we must go to Mass on Sundays, to offer the perfect sacrifice and perfect prayer which does more than any amount of other praying in this regard. This is also why at least some sort of penance is highly recommended if not mandatory in most places on all Fridays.
If you feel that your penance is too light then it means you’re being called to spend more time in private prayer and penitential acts is all. While extreme physical penances like severe fasting should be cleared both with a doctor and your priest or spiritual advisor beforehand, you don’t need anyone’s permission to spend more time in prayer or increase practices such as daily Mass (assuming you’re not neglecting work, study or other obligations to do so).
God has blessed you with an acute awareness of the harm that sin does, but the remedy for that doesn’t necessarily lie in the penance imposed in the confessional, my friend.