Unable to pee!!

Is it normal to not be able to empty your bladder? I find myself having to urinate very often and it will only be a very small trickle when I do. I try to push out the remaining urine in my bladder because the "need to pee" feeling is still there but it just won't come! I had one night when my bladder was so full, I was in tears, scared I'd have to go to the hospital for a catheter!