No, not from pee. Fresh semen from an ejaculation has to get in there. If you were four months pregnant you would have a long list of early signs other than a missing period. One missed period is not unusual. Four missed periods calls for a doctor checkup.
Oh hon. You need even just a basic sex Ed course. When I was a kid, girls used to think you could get pregnant from sitting on a toilet seat. That is until grade 8 sex Ed. Please, please get informed on the basics.
I bet there is even reputable sex Ed courses on the net. Take one hon.