Lower back pain. Sound in same location!

I feel pain in my lower back middle just above hips and weakness in legs if I stand still for more than 5 to 10 minutes. If I walk no problem but cannot walk for too long.  Whenever I get pain in lower back after standing still for 5 minutes I lay down flat in sleeping position with my back on floor or my left or right side on floor or bed . After 10 to 20 minutes my back pain and weakness in legs disapeares and I will be back to normal. I have frequent stomach problem like IBS along with anxiety and OCD. I'm taking medication for hypertension ie Metalar xr 50 mg 1 tablet per day. And for anxiety some times I take petrol MD whenever I feel very anxious or panic only. Whenever my stomach upset I take Ornidazole followed by Darolac . Please tell what may be cause of my back pain if I stand still for more than 5 to 10 minute.Im single addicted for masturbation more frequent in teenage but now 2 to 3 per week now. when i ejaculate i feel strong contraction with click sound in same location