I just dont see how a supplement could cause that. Like, with a lot of supplements like Tribulus, Yohimbee, gensing, maca, etc, they actually would have a positive effect in that department. A lot of pre workouts have these and should actually help cause they increase testosterone. I supose its possible for an ingredient to have the oposite effect but i doubt it. Obviously tho, if your saying others are complaining about it, maybe I would switch to something else

I really think its due to be worn out tho from your workouts. when your really tired, due to lack of sleep, im sure your libido is lower than when your fully rested and right before a workout
Well you are definately overtraining brah. I mean let me elaborate a little.
If your doing a set and waiting 5 minutes before the next set, that is going to take up lots of time, and by doing that I dont think you would be overtraining even if you spent 2 hours there. Also if you have a partner, and are waiting for them in between your sets this will also increase time, and id say 2 hours if fine.
However, if your like me, and you go hard in the paint, with 120 seconds between sets and exercises, then your probably overtraining.
I have a Leg, Abs, Chest/tri, Back/Bi, and Shoulders day. thats 5 workouts a week. (I do abs once a week, because I believe your abs are just like any other muscle in your body, and if you over work them by doing them multiple times a week then they will get real lean and flat which is good for some I guess, but if you work them once a week and go hard they grow huge, and stick out like fists and I like having abs like that, so I am using this method to continue their growth in looking HUGE lol). Also you have to figure, when you do some of your other trainings like dead lifts, and squats, you are still using your abs cause they are stabilizing muscles, and if your getting them worked out then, and 3 other times a week, its almost like they get no rest at all, aka will never grow big
I do 15 minutes of cardio (interval) usually about 1.5-2 miles after my workouts.
I average about 1 hour and 5 minutes.
Today I did
5 x 15 sets of shrugs
3 x 15 shoulder presses
3 x 15 shoulder raises
3 x 15 bushwackers
15 minutes of cardio / 1.5 miles.
it was my shoulder day, and any more than the above would probably be overtraining. My shoulders were killing me and I was feeling pretty worn down.
Previously I was on a strength training regemine, and was doing heavy weight and less reps, and that was much easier. keeping things moving for 15 reps is really stressful for me right now, and is helping me get my stanima back, while maintaining my strength gains. I am also doing this for hypertrophy reasons, and adding muscle mass, instead of strength (body building over weight lifting

)
But at the end of the day its really what works for you.
The thing I do want to say is they have done many studies, and they have taken people who workout 6x a week and compared them to the people who work out 3x a week. the people who worked out 3x a week actually put on more muscle mass than those who worked out for 6.
Interesting I know, but I think it has to do with overtraining. Every time you go hard, your nervous system takes a shit, and if you go hard without allowing your body a chance to recover, the efficiency of the recovery is reduced.
My issue is I dont know what to do with myself when I dont go to the gym or do some physical activity, so thats why I go 5 days a week. I should take a rest in between, but usually Mon-Fri I workout and weekends I party and eat / drink what I want.