Okay- well, no medication is good, however, the bike riding and/or other things could have caused damage over time. The only way to know for sure is to go to a neurologist. I would definitely recommend doing this before proceeding with a sex therapist.
Other ideas - supplementation with DHEA (health food stores) can help with sexual issues.
Finally, studies have shown that even moderate bike riding (e.g. commuting) can result in arterial blockage over time, leading to ED. Just FYI.
I hope this helps a little!