Finasteride, in my decade of taking it, hasn’t really affected my sex drive. I had alot of testosterone however, and respect the fact some men do get sides.
However, finasteride inhibits about 85% of your type 2 created DHT. Adding nizoral shampoo about two days a week because of its suppressive effect on androgen receptors and interruption of some inflammatory pathways) will aid finasteride.
If you get on both, you will have a shed period in all likelihood between months 1 and 2, then your hair will gradually begin to rethicken for up to two years, then it should hold the line or very, very slowly thin for the rest of your life.
I have lost some hair on finasteride in terms of temple recession, but its been slow. The hair on top and in the back is thick.
There is a chart on propecia.com that shows you what you can expect with finasteride ALONE. Hair counts go up for two years, and start to lessen, but they lessen very slowly, not anywhere near what the placebo group did.
IF you really want to keep what you have up there, get on finas, and use topical spiro 2X a day where you are thinning the most. Its a receptor blocker, and coupled with finasteride would cut androgenic stimulation down to extremely low levels.