Yep, still nauseous and throwing up at 21 weeks. I did the same with my first pregnancy as well. :(
Unfortunately some ladies do get nausea or other symptoms throughout their entire pregnancy.
Yes it is normal. I am 31weeks today, and my nausea has also returned. I had very bad all day sickness till about 24 weeks, so I am just grateful I had a break in between, hehehe.