BBT while Pregnant?

I have had 2 blood tests that have confirmed I am 4 wks pregnant. I had a mc months ago so I am paranoid and cont. to chart my bbt. It is still above the coverline (which is 98 F) but seems to be staying at 98.4F. Last week I had higher numbers 98.6 and 98.8. I go in for my last blood test tomorrow (they just want to make sure my hcg levels are doubling). Once you are pregnant should your bbt cont to rise? Are bbt and hcg linked? I know not everyone sees a triphasic pattern, but I just want reurance that my consistant pattern was normal. Anyone with a similar experience. I don't really have any pregnancy symptoms.