I am 27 and just had my first baby, but even I had these types of feelings at times. Really, I think ALL moms have those moments when we almost wish we were back in the "old days" before we had children. But then, we look at our kids and know we would never give them up. Feeling that way once in a while is natural, tho.
You made a huge life transition, and you were very young, so you will feel some doubts. I think you sound like a GREAT mom, though!!
I agree that you should keep your dreams. Lack of excitement could mean that you are yearning for something more each day. Just because you are a mom doesn't mean you are JUST a mom ~ you are still you, your same ambitions, dreams or goals are still within you.
If you are interested in college, which is a great way to grow yourself and gives you a goal to work towards and can be exciting, online classes are definitely a great choice.
I am a stay at home mom with my one year old, but I take online college course with University of Maryland UC. (UMUC). I plan to teach. Taking classes is so fulfilling to me, I love it, and I love the interaction with the students online. It helps me to remember who I am besides just mommie or just wife. It is something ultimately to benefit us all, but really is for me.
If you decide to possibly work part time and put baby in daycare, that also would allow you to have some time out of the home in professional environment. Then you can recall some of yourself. I know it's work but it's still you-time without caring for baby 24/7.
Whatever you do I wish you the best luck!!