Well there’s not really a simple explanation, however, what you’re experiencing is common.
Levels of calories, protein carbohydrates and fat in the diet can all have effects on the endocrine responses within the HPT axis. Severe calorie restriction, whether from reduced food intake or imposed by excessive exercise, lowers testosterone.
Now the question I’m going to ask you is - why are you cutting? In another thread you said you were 5’6 and 135 pounds at the age of 21. (If I’m wrong please correct me)
The last thing I would be doing right now it trying to lower my bodyweight. If anything you should be looking at changing your body composition - which means keeping your calories near or slightly above maintenance levels while changing the macronutrient ratios to facilitate muscle gain and fat loss.
Judging from your decreased sex drive - it sounds to me like you’ve dropped your calories too low.
Ideally with the right foods you could be eating upwards of 2500 calories a day. (if you’re distance running - as per the “guru” thread)
In regards to “why am I cutting”, It’s more so that I WAS cutting, which is how I got down to that weight…but now I’m kinda at the point where I’d like to bulk up a tad, but mentally I just can’t get past the “having to probably gain some fat along with the muscle at first” thing…