I am a 24-year-old man who can't come – do you have any advice for me?

   

 I'm a 24-year-old man and I can't seem to achieve orgasm with a partner. At first I thought I might be gay but I tried sex with a man and I still had the same problem. I really don't know what to do. It makes me feel powerless and less of a man. This happens about four out of every five times I have sex, and when it doesn't it can still take me 40 minutes to achieve orgasm, which is ridiculous at my age. I am ashamed and very depressed.