First things first. If you have unprotected sex, there is a possibility of being pregnant. If you're nauseous, there is a possibility it's because you're pregnant. Or, your nausea might be caused by the same thing that's giving you killer gas. (gas, by the way, is *not* a sign of pregnancy.)
and, umm, maybe sex was painful because you were having it every single night for a week. Just a thought.
When you're playing the "am i?" game, every tickle in your throat will make you think it might be a sign. The only way to know for sure is to get tested. Until it's time to test, you just have to wait. In the meantime, you can .Google "pregnancy signs" and compare notes.