It's pretty rare to get nausea that early in a pregnancy but I have heard that it can happen. Generally it doesn't hit til after about 6 weeks when your hormones have had a chance to really get going. I haven't suffered from m/s at all though so I'm not probably a good example. I did however get a BFP at I think it was 10DPO after I'd noticed bleeding gums which isn't supposed to happen that early, so anything is possible. Best of luck.