i am a married man with children, but are some circumstances that push me into this act. some times my wife does not surrender herself or make herself available when i really need her for sex. secondly, i engage in this act during the breastfeeding period because my wife can never allow to come near her during this period.
It appears that your question is about masturbation. I do not believe that masturbation is strictly prohibited in Islam (as discussed here: Masturbation is not clearly forbidden or allowed in Islam), therefore what you are doing is not a big issue in my opinion, even though I believe that a great man would always avoid masturbation regardless of the temptations and unsatisfied needs.
If you feel guilty about masturbating, you can do an act of worship to make up for it, such as reading the Quran for an hour, or giving away a certain amount of money, after each time you do it.
If you masturbate, it is best to avoid using pornography for that purpose, as that is a far more questionable thing to engage in. For more on pornography please see: The Philosophy of Pornography and Masturbation