bbt question

So I took my temperature whe. My hubby woke up at 4am and it was 96.8 and I didn't get out of bed I hardly even moved and then fell right back asleep and the. Took my temperature again when I woke up at 6am and it was 97.8........ does the temperature really differ that much and what temperature should I go by....I got my LH surge yesterday morning so I am looking for the temperature increase and just wondering if this was it or not yet.... pretty confused because most mornings I do take my temperature twice at those times just out of curiousity and it's usually the same or maybe .1 degree difference now a whole degree