If you can see eggs then they have been fertilised by a male. Eggs that havn't been fertilised are represented as a "saddle" higher up the female.
From experience, females will "yank" their eggs off their pleopods (swimming legs) in about a day if the eggs are infertile. The eggs don't always get fertilised even if you have males. If they carry the eggs for beyond a few days then it's quite likely that you have little shrimplets hiding somewhere. It takes about 3-4 weeks for them to hatch. The babies are very good at hiding and quite invisible.