plz think if u were me

I started masturbation followed by ejaculation only at the age of 18. But ejaculation was possible only when i rubbed penis over the bed wearing my normal cloth. From age 18- 19 and around 10 month, i used to ejaculate playing with my neice and other chidren permitting them to play on my laps( both children and me were wearing normal clothes). Then after i realised that this is bad and i stopped doing these things even though these children requested me to play with similar style . At that time i still remember that these children were very happy and i had done no harm with them. At present i am 27 years of old age, the childrens whom i used to masturbate have grown now, they all are perfectly healthy. I am 99.95% sure that they knew nothing about such incident. I respect the children . i want to save the children from such kind of abuse. But,When i hear about childsexabuse, i feel guilty about the act that i had done in the past. I swear i did not know that the act i was doing was a kind of abuse. plzzz give me advise that what should i do , how big crime have i done and what punishment should i get?