Frequent urination

[tiredpoet]

Hi there.  I am a 33 year old female, 5'3", 110 lbs, and I have fibromyalgia and a clinical diagnosis of Lyme Disease (no positive blood test).  I've had a lot of symptoms for over five years, one of which is a problem with frequent urination and feeling the urge to go immediately after voiding (I mean immediately, before I even leave the bathroom).  On a good day I will be able to hold it so that I only go once every 1.5 to 2 hours, but sometimes I have to go every hour, and when I drink anything, if I don't sip it slowly but instead take in several ounces at one time, then I will literally go immediately (about 5 minutes after drinking) and have to go 3 times in a half hour.  I now barely drink anything all day because of this.  For instance, today I just finished a 16 oz bottle of water that I opened 5 hours ago.  I have urinated 6 times, all 6 times the urge to go was very strong and all 6 6 times I only urinated a little bit of clear urine--and that 16 oz bottle of water is the only thing I've had to drink all day.
At night it's worse.  I will go, stand up, feel like I have to go again, so I'll sit back down and "trickle" and then go to bed.  15 minutes later my bladder will feel extremely full, and I'll go back to the bathroom, where I'll void a very small amount of urine and still feel like I have to go.  If I just stayed in there I would probably void a tiny amount of urine (probably not even 1/8 of a teaspoon) every 10 minutes or so all night. Sometimes I'll wake up between 3 and 5 times during the night.
Sometimes I feel pressure in my bladder, but I wouldn't call it pain, and the urine is usually clear or just slightly yellow.  It never hurts to pass, and I've had a few negative UTI tests.  I've never experienced any leakage either.  I just go a lot and usually don't feel like my bladder is completely empty.  Do I just have a small bladder, or is this normal?