I have the same issues, though I have had my swollen tonsil for damn near my whole life. I've been diagnosed with sleep apnea, due in large part to the massive tonsil on the right side of my throat.
One doctor told me that my tonsil was swollen due to allergies, though I've recently been reading that it's unlikely that allergies would cause just one of the tonsils to severely swell.
I'm going to schedule an appointment with an Ear, Nose and Throat doctor to have him take a look at it. I understand that the older you get, the more risky a tonsillectomy becomes; however, I'm sick and tired of being sick and tired at 24 years old, and I think it may be time to have those suckers cut out.
To Willethin, I would also suggest seeing an ENT doctor, as they specialize in staring at tonsils. It's better to get on top of it now, rather than end up chronically fatigued from lack of sleep 3 years later like myself! Good luck.