Hi, I Am An 18 Year Old College Student. For

Hi, I am an 18 year old college student. For about a year now I have been noticing a low libido in myself. I cannot get a hard erection and I do not wake up with one. I had my testosterone levels tested and they're normal. I just want to know why I don't have as big as a sex drive like i had when i was a few years younger and why when i get erections they aren't as hard as they used to be.