I've been lifting fairly intensively with free weights for about 18 months now, and have put on 45 lbs. of (mostly) muscle ... I'm now 200 lbs at 5'7". I lifted using weight machines, much less strenuously, for about 8-9 years before that.
My wife and I have honestly noticed no increase in cock size (which is fine given where I already am down there!) What we have noticed is significant "gains" in certain aspects of my sexual performance, most notably cum quantity and the distance/force of my ejaculations. While I can't be 100% sure that my muscular growth or protein-rich diet are the cause, I have to assume the lifting and related lifestyle changes have played at least some part, given that at 31 I am somewhat past what is normally considered the peak of male sexual performance.
As far as how horny I am, it varies greatly with the intensity of my lifting during a given period. At times when I am killing myself by lifting 5 days a week for 1-2 hours a day (on top of 30 minutes of cardio), my sex drive is really pretty shot. By comparison, if I lift only 3 days a week for 30-60 minutes, my sex drive stays quite potent.
For specific guidance on how to gain muscle mass, I'd suggest you retain a personal trainer. Everyone gains muscle differently, and you can get the best personalized guidance by working with a knowledgeable professional. Another very good resource is Arnold Schwarzenegger's "New Encyclopedia of Modern Bodybuilding," which is extremely informative and comprehensive (even if you're like me and don't want to bulk up to true "bodybuilder" levels). You can get it on Amazon for about $18, I think.
Steve :smile: