nausea already?

My husband and I are TTC for #2. We did the deed literally 4 days ago and I'm already nauseous. I was ridiculously sick with my first and felt like the second I got pregnant with her, I was nauseous and had to eat every hour to keep the nausea down. Then I hit 6 weeks and I wasn't able to keep anything down and ended up on nausea medication. This time around, I can't afford to be that sick because I have an 18 month old to chase after. But I still won't know I'm pregnant until at least the end of this month.