99 is pretty high for a BBT. Have you been charting long?
I've been reading DPO symptoms from women that later got BFP's and several of them mentioned temperature drops at some point.
Check out this site: http://www.twoweekwait.com/bfpsymptoms/dpo/index.html
I'm just wondering if there's some kind of hyperthyroidism going on. Both hypo and hyperthyroidism can lead to fertility problems.