from what i know and experienced (because i am using FSH & LH) FSH has nothing to do with libido,unlike HCG which some people reported noticeable improvement in libido.
fsh is good, to keep your fertility as TRT doesn't only drop fsh it pretty much shutdown your gland,,, meaning no LH and no FSH, if you don't take LH and FSH you will lose fertility, some don't take FSH and can still have sperms, but having FSH and LH both you will have sperm 100%.
the only way i have good libido is every 3 weeks i stop HCG (LH) and i get nice libido which last sometimes for 2 weeks. then it goes away and i repeat this.
i read people saying libido has to do with many factors not only one factor.
also a side note there are many trt users which have libido issues so your not the only one.