The same thing happened to me. Previously around 97.8 before ovulation and 98.3 afterward. I just treated it as two charts.
After about 3 months, however, my pre-ovulation temps finally rose above 98 (avg. 98.04). It actually caught me off guard because they didn’t drop enough for me to be prepared for my cycle LOL!
I think it’s a slow process to get your temps right, and for women it takes even longer because you have to keep switching back and forth to accurately see a pattern.