Next car seat?? LOST!

So, I have a car seat that I was given in a program I was in before I had my baby. It's an infant car seat and the height limit is 29in. He's already 25 inches long, so I'm gonna have to get him a new one soon. The thing is, I don't know which one the new one would be! What I mean is, I don't know which one would be a "next stage," rear facing car seat. Since they're supposed to be rear facing for as long as possible. My little one is quite long/tall for a 4 month old, imo, so I don't know which one to choose. For my oldest, I didn't have a car after she pretty much out grew the new-born car seat. Not until she was about to be 2, so I have no clue as to which car seat comes next. Right now I have this one, which is the one I got in the program. It's super light weight and easy to carry my munchkin around in from the house to the car and when I have to go to an appointment or something since I don't have the stroller for it. I just feel dumb cause I don't know what's next. The ones I've seen aren't rear facing ones and that somehow worries me a lot.