Scared Of The False Positive

So today is day 16. Day 16 that is from when I took my HCG injection. My Ob Dr told me to wait at least 14 days after the inj. to take a pregnancy test because anytime sooner has a higher chance of giving you a false positive. I was fooled once before because I once took a pregnacy test on day 11, because I was really anxious and couldn't wait, and then got disappointed when it was positive then only to turn negative on day 14 with my period to follow.
So being past day 14 I took a test today. The big fat positive showed up right away and I immediately ran upstairs to go show Dereck. I'm so afraid of the false positive happening again though. I decided to google "when to take a pregnancy test after an HCG inj." to see what was said about it since my Dr.'s office isn't open. Three different websites confirmed that usually you are fine by day 14 but that sometimes it takes up to 20 days for it to be out of your body. Eeeeeek!!!
I also have been really tired the last 4 days. I have been going to bed by 9, which is very rare for me except for when I pregnant last time, and have been sleeping about 10 hours and still tired all day. I have had a few other symptoms also but I feel like it's too early to be getting pregnancy symptoms. Plus, I was just on vacation and could be exhausted from that, or just sick. I just want so badly to be pregnant again, I waited the 14 days, could I actually be pregnant? Guess I just have to wait a few more days and test again, unless my period decides to come first.