Still bfn.

Took my second weeks estimated test this morning fmu and it was "not pregnant" I'm getting back pains more often now, still having cramps every day but not too bad. Not really having an appetite for foods just wants sweet & salty stuff. Had 3 faint positives last week. Really scared, just wanna get a BFP ...we've already gotten excited. Anyone else go through having to wait till further along in their pregnancy to get a BFP but still feel pregnant or have to have a blood test done to find out due to previous miscarriage?