Can something change your heritage?

Hi!
I would ask that can that dna change in your life-time that passes to your children or I dont know exatcly what its called that passes to your chilren,but it is possible that your heritage can change in anyway from life-events,drug use,cigarette use.
I have heard that taking SSRI´s can change your gene expression or dna or something,can those things be seen on my future´s child ancestry.I have tooken SSRI´´s and other mental healt medicines for my depression.but I have been really really short time on them.
I also heard that re-actional drugs can alter your dna.I hope that they wont be seen on my chilrens.
I hope you understand,since its somehow hard to explain,but my main question is this that will my heritage stay the same as my whole life-time or does it change from different issues?