I just can not think in any other thing that he getting STDs hahaha

Why would he get an STD? These women are clearly screened and carefully selected from billions. Of course they'd be tested for anything that'd potentially harm one of the last surviving males.

Not to mention we don't know how far medical technology has advanced. They were able to cure his MS, after all, a nerve-degeneration disease. What would a few STDs matter compared to that? They might have eradicated STDs in this future, like Smallpox and Polio of today.