Bfp 10dpo bfn 14dpo?!?

Montana
In Friday 10dpo I got a bfp strait away with morning urine using a test from eBay. So I went out and bought a clear blue digital test and the next day It was bfn. Today at 14dpo I also tested negative. Anyone think I had a false positive and the eBay ones are dodgy? Coz I doubt I would be pregnant now I'm registering as bfn 4 days after my bfp 
​Thanks for reading :)