My question to you is why wait until the 20th to take a pregnancy test? When I was pregnant with my children, I took the test about 2 weeks after I thought I was pregnant. It turned up positive each time. Maybe I produce more hormones than normal ( I got severely ill for 3-4 months), but my thought is that it can't hurt to do something about it now. If it's negative, of course you'll have to take it again.

I make no judgements on the choices people make, but I do know that the earlier you know, the more options you have. For instance, you can take a strong dose of hormones before 7 weeks in (I think that's the time frame) to terminate the pregnancy.

Good luck.