HMMM this has me stumped....
It COULD be a new pregnancy in the very very earliest stage. The only way to know for sure is to go for another beta

If it's back up there, then most likely you are PG again. The timing of BD seems to be right. You most likely would have gone to 0 ...Oed and then got pregnant causing the HCG again.
Or your body could just be trying to drive you bonkers
I vote (and pray) pregnant