Hi I am 30 and I am unmarried, 3 months before I got pain in my belly button when ever I go urine. I thought it happens because of eating non vegetarian, so I stopped it. After that it was OK for some time, but now if I touch my belly button I fell itchy and the itchiness reflects in my penis as well. Please advise me.

You need to see a Physician. Vegetarian diets do NOT cause pain. I know. I was vegetarian for a number of years.

Are you (or were you) sexually active?

No I don't involve in sexual activities. When ever I eat spicy food or non vegetarian I feel such itchiness and slight pain. Is it a sexual disease?

Could be many things, bladder infections, kidney issues,
If you were not having sex it would not be a STD.

Time to go have a check up.