Precum on underwear I touch wet trousers n then finger rubbing 5 minute her body then into vagina what r the chance of precum been in finger n pregt?

Not likely. It sounds like you were playing with fire. It's very simple. If sperm gets in the vagina at any time and for however long and in what ever way it got their pregnancy is theoretically possible. If it's been less than 72 hours consider taking plan b. Use a condom next time and avoid scares.