Are you male or female? This could make a major difference in diagnosis.
Hi
There is a possibility that something is obstructing the bladder neck like a stone, benign hypertrophy of prostate, polyp, tumor etc. Hence, once the pressure of obstruction is lifted off in certain direction the flow of urine starts. It is difficult to comment beyond this at this stage. You will need to consult an urologist for this. Please let me know if there is any thing else and do keep me posted. Take care!