What Could Cause My Libido And Morning Erections To Decrease, And Can Having Sex Restore Testosterone Levels?

hello, i m a 20 years old guy. around 6 months ago I experienced an increase in my libido, I had a lot of unwanted erections and almost every day I had morning erection. but i m single and never had sex. after that my libido and my morning erections started decreasing. now I have some symptoms of low testosterone, what happened for me? sometimes I feel depressed, I have morning wood just once a week, I feel pain in my legs while cycling. what happened to me? how can I fix my decreased testosterone? by having sex?!