OK, this is the nth time I am answering this - people, PLEASE check out the Questions and Answers Sticky before you make a new post - maybe your question has already been answered.
Om DID NOT marry Trishna. Trishna loved some guy who died. Because of that she went insane. Her father was Om's business colleague and for some reason, to help him out, Om PRETENDED that he married Trishna. There was never ANY relationship between them - not physical, not on paper, or any other way.
I hope this clears your confusion - but seriously, this is like the 100th time I have answered this for someone - please check the stickies and direct your questions there. Thanks😛