Maybe twins? Idk!!!

So last night I took a pregnancy test, and as I was wiping afterwards, I noticed some very light spotting. I know it was just implantation bleeding (no bleeding at all since, just that one swipe), but I've read that there won't be enough HCG for a pregnancy test to be positive until at least 2 days after implantation. So I was expecting the test to be negative, but lo and behold, the test was DEFINITELY positive. The second line was very dark. Just wondering how it could be this dark so early??? Anybody have ideas? ...maybe twins? (I'm a fraternal twin so it runs in my genes)