Yeah, you'll just have to wait and be patient till it hits the 7 to 8" range. Thats when they start showing their male/female traits.... Generally by the time they are 10" you should be able to tell if they are male or female...lol. Anything below those sizes would mostly be an uneducated guess...UNLESS you have multiple pikes of the same species. Almost 100% of the time the males will out grow the females. So the ones that get larger faster, are the males...
An inch or so a month is generally average for most pikes. Some are a little faster, some a lot faster, others slower. Just depends on the feeding, the tank size, and the amount of waterchanges...