BBT Thermometer Issue

Hey ladies!

I bought a bbt thermometer as instructed by you all back at the end of November and have been temping since. Well this month I noticed that I have had the same temperature several times (97.45)...I'm talking 2-3 days in a row. This morning I got the same reading as the last 2 days and got a bit irritated so I decided (no I didnt log it nor did I move around) to try a vaginal reading and got a temp of 98.15. Wtf

Has anyone experience this issue?

Do I need new batteries already?

Should I just get a whole new thermometer or something?

*No I dont plan to do anything switching til next cycle, no my hormones aren't that stale (97.45 is low for post ovulation) and yes i know vaginal readings are higher than oral, i was just seeing something.

Thanks and baby dust to all!