Implantation Bleeding or not?

Alright, so I'be been trying to have a baby. We wouldn't be actively trying, but we don't use protection either.. I want to have a baby so bad, and he's okay if it happens. Weird, I know. My periods are weird.. I worry I won't be able to get pregnant because they were so irregular before that I had them almost every day for 5 years. Then they were fixed for a bit when I tried birth control, and then it was gone for 4 months, and then back for 3 and a half months, and haven't had one since January 10th 2015. 

ANYWAYS! Abut a week and a half after we had sex, I started to bleed.. But it was so light, and almost brown all the time. Sometimes pink.. the odd time red. So I did my research, and it totally sounds like implantation bleeding. Test came back negative so far, but it is probably too early. Thing is though, it's been a week of this. Is that normal? The blood was red one day, which made me sad, but then it changed again to barely nothing, and brown.

Is it possible that it could still be implantation Bleeding?  It's most likely lasting this long because I haven't had a period for 4 months, so I get that, but this is soo confusing, and I really, really don't want to get my hopes up, in fear that I will be wrong. Again.

It would make me so happy to even hear some advice, or similar experiences, or even just some support!