What's the difference between implantation bleeding and a period?

I already asked a question related to this, but I'm still unsure of some things. On January 16th I had slight unprotected . It didn't last long and he didn't . However, I know that even pre can get a girl pregnant. My period normally starts at the end of the month, ranging between about the 27th-29th. It came on the 28th in December. In January, I got it on the 27th. It stayed light for two days when it normally only stays light for one. I normally have a very heavy flow and all together it usually lasts 5 or 6 days. So in January it was light for two days but then it did get to it's usual heavyness and then stopped on February 1st, which was a typical 6 days. My main question is how do I know if it was my actual period and not implantation bleeding from being pregnant? I keep being told I'm just being paranoid about being pregnant. The only other sign of being pregnant that I might have is my are really soft and squishy, and I'm pretty sure they normally aren't this squishy. But I don't feel more tired than usual and I'm not eating more or peeing more, that I know of. I just really don't want to be pregnant and I'm scared. I've taken three home pregnancy tests, all came out negative. But from what I've read, they could be false negatives. Which scares me even more. If I knew the difference between implantation bleeding and my period, that might put me a bit more at ease. Though this whole thing with my s really freaks me out, even though I've been told I'm just being paranoid and think they feel different. Can someone help?