Fluctuating sperm count

My husband has had 4 semen analysis, all dramatically different.

Count was 19 million, to 8 million, to 18 million, to now 3 million.

Morph and motility all fluctuate too.

The worst one is after months of very little drinking, and taking fertilaid and motility boost. We thought it was working when we did the 3rd test and so he melt at it but the 4th test is now our worse yet. Any idea what can be going on?