I’m not aware of any medical condition which causes acid sperm and infertility. The usual pH of the ejaculate is between 7.2 and 8, so it is a little alkaline, and sperm seem to survive best in the laboratory if they are kept at this pH. Increasing the zinc concentration in sperm is said to increase the acidity, but it’s doubtful if this has any effect on fertility. Drinking bicarbonate of soda will make the urine more alkaline and we use this technique for men who have had a vasectomy and therefore ejaculate backwards into their bladder. We can then extract live sperm from their urine. Other than these facts, I cannot offer any further suggestions.