Two things:
One, if you are lasting 45 minutes, raw, why are you kegeling? That’s alot of erectile capbality.
Two, OVER exercise of any body muscle causes temporary weakness.
I myself can be compulsive about muscle training. When I was younger, I always was strongest after a week’s vacation because I was forced NOT to overtraing for seven days.
Without enough rest time, muscles will grow very weak and sore. Stop kegeling for one week and see if you don’t last over an hour in bed(that is, if your lover can stand it). If you are much improved by the long rest, chances are you have been overtraining your pc muscle.