Dear mikoblume, TOO much heat exposure for long time as workers near furnace , steam boiler in industrial use affects sperm count
not 5 -10 minutes of hot bath its myth, no way it decreases testosterone
levels in healthy normal man. as you are concerned about your fertility
get checked your sperm count that will give clear idea regarding your fertility potential don't make assumption. lot of things in media and road side literature about sex gives wrong information consult a qualified Doc. as you get your semen analysis
done. Do abstain from sex for 5 days before doing semen analysis.