Positive Test and then 3 Negs. Still no AF

I had some brown tinged CM 12 and 13 DPO thought my period was coming then nothing since. Could it have been implantation bleeding? My Cervix feels hard. I took a HPT yesterday and both the control and test lines were really light but there was a positive and it showed up within a minute. Took another test 2 hours later BFN. This morning I took another 2 tests this morning and both BFN. Still no AF. I am now 16DPO. I am thinking of buying another Brand.. What do you all think is going on? Am I pregnant?

what brand were they

I love the first response tests and very accurate.

maybe wait till you havent been to the loo for a good while so your wee is concentrated.

good luck

They are ones I got off the internet. They are meant to test 15IU?? I was thinking of trying FR people seem to be confident with them. I did my first and second morning urine with the 2 test this morning. Argghhh!! This is exciting but I just need to know!! Thanks for your reply.