If I didn't have facial hair til18years old and I was very skinny. At age 35 for the first time I checked testosterone is 150. deficiency since birth?

Low T since birth. There are certain genetic disorders that cause deficiency in testosterone. If you went through puberty, then you had enough testosterone. If you are obese, then low testosterone is likely from your fat cells converting testosterone to estrogen (female hormone). Exercise, eat less, lose weight, and a lot more improvement in your overall health will occur.