Paige,
I envy your study of Shaolin. By the time I got around to studying martial arts, I felt that my body was so worn out from life that every other MA out there would only injure me more. Aikido has been good to me, keeps me in shape and I enjoy it... so I'll stick with what I know.
I'm sorry to hear your not progressing in aikido though. Two classes a month isn't going to get you anywhere, whether rank matters or not. Had I been in your shoes when you first started this post, I would have approached the Sensei and told him/her my concerns and gotten feedback on it. Sure, kids are graded differently than adults, in various martial arts... and I've often wondered what a 12 year old "black belt" would think when they finally turned 16 or whatever age and were handed a kyu rank belt? I'd be a bit peeved to.
You mentioned a competition with your Shaolin MA, and if you enjoy tournaments, you might be in the right place. Personally, I like aikido because I do NOT want to compete. I'm not here for the rank, ego or anything else. I like learning a skill that will help me protect my family, loved ones and self. I know that going to class will get me and keep me in shape, develope balance and endurance I've not had for over ten years and give me a confidence so I can not worry about a lot of different things.
Aikido has given me something else I really enjoy: Wisdom. My mother had fallen a week ago and could not get herself around, couldn't stand hardly, go to the bathroom, none of that. Through my knowledge of Aikido, I found a way to lift her and safely move her from room to room without injury to myself or to her. I even got some "knee walking" in through the process. Anyone else would have had to call 911 and get medics to move her around, but she didn't want to make a "big fuss" over her situation... spared her some embaressment.
Do what is right for you. Learn all you can and enjoy and be sure you are where you are for the right reasons. I think if I were you, I'd shop around some other dojo's and try them out, talk to other instructors and see how they do things. If something at your aikido dojo upset you and caused you not only to vanish off the mat, but change arts altogether... perhaps it wasn't as great as you first thought??? Don't want to speak ill of your Sensei... but it might be something to consider.
Good luck to you! Let us know if you win your tournament!