It feels as if there is a tiny penis inside of my vagina. When I took my first trip to the gyno, she didn't say anything was weird... so what is it?

Most likely, it's just your cervix.

The cervix is the end of your uterus, or the beginning, depending on how you look at it, and the cervix and cervical canal jut into the back of the vagina. When you're not highly aroused (arousal usually will pull the cervix further back), you can usually feel it by placing your finger inside, and given that it is a bit tubular, and also has a small opening on the end, it's easy to see why you might think it resembles a penis.

Next time you're at the gynecologist, you can even ask him or her to take out a mirror when they're doing your speculum exam so you can get a look at it: it's a pretty cool thing to do, and will likely clear things up for you.

For more on your sexual anatomy, have a look here: Pink Parts - Female Sexual Anatomy.