Is it possible that I have cystitis? My bladder feels lower, fuller.

Can be/other symptom. Cystitis has many infectious causes, and symptoms. The usual ones are dysuria (painful urination), frequency, urgency, and suprapubic pain. But it can be asymptomatic. Depending on your age, etc. Other things, like weak ligaments that hold up the bladder, uterus, and other organs can cause fuller/lower feeling bladder. However, it can be cystitis and you should see your doctor to rule it out.