Can i be pregnant if i was on top during unprotected sex and 5 days after that am feeling nauseated and cant keep breakfast down?

You can get pregnant from unprotected sex in any position. However, 5 days after a single episode since your last period, you are unlikely to have symptoms that soon if you did get pregnant. You could be pregnant already, or something else is going on, including a possible sexually transmitted infection.

Conception occurs within day or so of the sex. It takes about 3 weeks for the embryo to make enough HCG for a positive pregnancy test. Blood test may be done a day after a missed period. Home pregnancy tests should be done 4-5 days after the missed period. If the result is negative repeat the test in 4-5 days. Use first morning urine and follow instructions for the test carefully.

Yes. Unprotected sex from any position, can lead to pregnancy. Morning sickness can be a tip off (though the nauseated feeling alone can also be due to other reasons). 5 days later would be rather early, but people vary and there can be exceptions to most rules. Also, possibly the pregnancy occurred at an earlier time than thought. If concerned, you should have a pregnancy test.