I think i have low testosterone/delayed puberty/it's something abnormal!?

i'm 18 and i dont look 18...i'm 5'10 and about 150lbs, as for bodily hair i do have it in the pubic region, lower legs, barely any under my armpits, it grows in light patches from the calves up, my voice is normal for my age, no substantial facial hair (barely sideburns) i dont know if it's relevant but my isn't really as hard as i think it should be....any ideas/tips/advice? please....