What can I compete in?

What can I compete in?
I am 19 years old... have been riding for 5 months.
My horse is 5 years old.. knows only the basics of flat work.. doesn't jump or do advanced moves ect.
We ride english in an all purpose saddle.

.... So.. what kind of classes are there for a green adult on a green horse? I always just see little kid classes for my level of riding

Dressage is a great prospect if you're not into jumping.

Dressage
Maiden/Green/Walk-Trot English Pleasure
Maiden/Green/Walk-Trot Equitation
Maiden Trail
Distance Riding
Showmanship
Halter

I would look for Maiden or Novice Horse classes. You can even do Junior horse classes (since he is a junior horse until he turns six).

Wanna do jumping eventually... just can't too soon.

What are these maiden classes?
And whats distance riding/showmanship entail?

Maiden is usually for a rider in their first or 2nd year of showing. Novice horse/rider is usually for a first year horse or rider. You get a little screwed sometimes because they'll put a thing on the billet that says something like hasn't run a blue ribbon... which means there will be people more qualified in that class... but it's all for fun in the beginining anyway right?

Maiden is if you have not won a first ribbon before. They usually have either Maiden Horse or Maiden Rider. So if you have never won a 1st before but your horse has, you could only enter Maiden Rider. Other places will do "first year of showing" or something similar.

Distance Riding is similar to Endurace Riding. The shortest I believe is 25miles and it goes up from there. You are judged on the condition of your horse, and being within the time limit.

Showmanship is an unmounted class. Here is a video: