bfp, then bfn, then bfp, then bfn... Help!

Hi everyone, I need some advice or if this has happened to you what the outcome was? I tested on morning of 10dpo, verrrry faint BFP. Then later in the day with a 4 hour+ hold and little to drink, I got a BFN. This morning 11dpo, another verrrry faint BFP (no darker than yesterdays). So same as yesterday I did another in the afternoon with 4 hour hold and then BFN. I'm still getting little cramps though. Do you think this is a chemical pregnancy?

My last PG I had a pretty strong bfp on 9dpo but that pregnancy miscarried at 14 weeks due to the baby having down syndrome plus alot of other problems :'( I read somewhere that down syndrome pregnancies can have higher HCG levels. So I'm discounting that as a comparison.

Any advice or has this happened to you?