SA results changing

Jennifer
Short story my dh had his vasectomy done in 2012 we had it reversed May 2015. Three months after the reversal he had 30 mil sperm per mL. We tried getting pregnant for about 6 months with no luck. February (9 months after reversal) we had his numbers checked again and it came back that his numbers dropped all the way down to 400 thousand. Yes you read that right 400 thousand. We started seeing a fertility doctor because we were so concerned (the same place we got all SA's done). The fertility doctor ordered another SA in March (a little after the 400 thousand result came back). Well this time it came back with 24 million per mL. At this point I am not sure why it was good then really bad then back to good. We have not changed anything. Also, the motility and morphology has both improved from the first to the last check. Has anyone else had or know anyone with this type of situation?