I think you might be missing the Matchmaker. I think she usualy comes in the evening, i can't remember what times exactly as i havn't been on here since Summer, but they generally come in the evening.
Keep your Tamagotchi close by you with the sound on so you will notice if she comes.
Is your tama an oldtimer? If it is, you won't get the matchmaker, and the only way you can get babies is marrying the oldtimer of the opposite gender. But if you happen to do that, the babies will become Oyajitchis.