It's very easy to sex buns. Mine are sex'd as early as 4 weeks and other more experienced breeders can tell at a day old.
Look at some tutorials on the internet, at 4 months they will be very, very easy to tell.
Pulling it out and eating it usually means lack of magnesium in their diet. As recommended above, Lobo had some good information.
If there is any sign of nest building separate them asap as said nest-building bun can and most likely will get very aggressive. Though this doesn't look like the case.
Look at tutorials and sex them asap. Obviously if they're male and female it's most likely the doe will already be pregnant.