Re: It's getting annoying..
In my current dojo our classes are mixed. We try to pair up with someone different for each technique. Sometimes you are pared up with a beginner and sometimes with a senior student, sometimes you do more teaching, sometimes more learning. It was the same way at Boulder Aikikai.
That said, teaching newer students is important. I think it is very important to help less experienced individuals create proper habits, correct stance, moving from center, proper angle, proper rolls etc. Give them the fundamentals to progress to the level that allows them to go all out.
I also believe every Dojo should teach proper Ukemi before teaching anything else.
If you you are worried about getting a workout perhaps an hour of P90X everyday would help.
Good luck, I really hope you get it all sorted out.