I have a weak urination. i feel the bladder always full even if i have just finish to urinate.no burning,pain or hematuria.what could it be?

Urinary frequency: Please see your provider to do a Urinalysis to ensure you don't have Urinary tract infection. A pelvic exam is not a bad idea either. if everything is ok in pelvic exam and UA maybe a cystoscopy to make sure you don't have interstitial cystitis, a condition that bladder is inflamed for unknown reason. losing weight, avoiding stress and spicy food and caffein might help.

Need to be seen: You need to have your residual urine checked(amount remaining in your bladder after voiding).This can be done by catheter or,painlessly,by ultrasound. If you are holding a significant amount the more tests are needed called urodynamics,cystometry...The urrine will be checked for infection. I would see a urologist. Best of luck.